fio - flexible I/O tester
fio [options] [jobfile]...
fio is a tool that will spawn a number of threads or
processes doing a particular type of I/O action as specified by the user.
The typical use of fio is to write a job file matching the I/O load one
wants to simulate.
- --debug=type
- Enable verbose tracing type of various fio actions. May be `all'
for all types or individual types separated by a comma (e.g.
`--debug=file,mem' will enable file and memory debugging). `help' will
list all available tracing options.
- --parse-only
- Parse options only, don't start any I/O.
- --merge-blktrace-only
- Merge blktraces only, don't start any I/O.
- --output=filename
- Write output to filename.
- --output-format=format
- Set the reporting format to `normal', `terse', `json', or `json+'.
Multiple formats can be selected, separate by a comma. `terse' is a CSV
based format. `json+' is like `json', except it adds a full dump of the
latency buckets.
- --bandwidth-log
- Generate aggregate bandwidth logs.
- --minimal
- Print statistics in a terse, semicolon-delimited format.
- --append-terse
- Print statistics in selected mode AND terse, semicolon-delimited format.
Deprecated, use --output-format instead to select multiple
formats.
- --terse-version=version
- Set terse version output format (default `3', or `2', `4',
`5').
- --version
- Print version information and exit.
- --help
- Print a summary of the command line options and exit.
- --cpuclock-test
- Perform test and validation of internal CPU clock.
- --crctest=[test]
- Test the speed of the built-in checksumming functions. If no argument is
given, all of them are tested. Alternatively, a comma separated list can
be passed, in which case the given ones are tested.
- --cmdhelp=command
- Print help information for command. May be `all' for all
commands.
- --enghelp=[ioengine[,command]]
- List all commands defined by ioengine, or print help for
command defined by ioengine. If no ioengine is given,
list all available ioengines.
- --showcmd=jobfile
- Convert jobfile to a set of command-line options.
- --readonly
- Turn on safety read-only checks, preventing writes and trims. The
--readonly option is an extra safety guard to prevent users from
accidentally starting a write or trim workload when that is not desired.
Fio will only modify the device under test if
`rw=write/randwrite/rw/randrw/trim/randtrim/trimwrite' is given. This
safety net can be used as an extra precaution.
- --eta=when
- Specifies when real-time ETA estimate should be printed. when may
be `always', `never' or `auto'. `auto' is the default, it prints ETA when
requested if the output is a TTY. `always' disregards the output type, and
prints ETA when requested. `never' never prints ETA.
- --eta-interval=time
- By default, fio requests client ETA status roughly every second. With this
option, the interval is configurable. Fio imposes a minimum allowed time
to avoid flooding the console, less than 250 msec is not supported.
- --eta-newline=time
- Force a new line for every time period passed. When the unit is
omitted, the value is interpreted in seconds.
- --status-interval=time
- Force a full status dump of cumulative (from job start) values at
time intervals. This option does *not* provide per-period
measurements. So values such as bandwidth are running averages. When the
time unit is omitted, time is interpreted in seconds. Note that
using this option with `--output-format=json' will yield output that
technically isn't valid json, since the output will be collated sets of
valid json. It will need to be split into valid sets of json after the
run.
- --section=name
- Only run specified section name in job file. Multiple sections can
be specified. The --section option allows one to combine related
jobs into one file. E.g. one job file could define light, moderate, and
heavy sections. Tell fio to run only the "heavy" section by
giving `--section=heavy' command line option. One can also specify the
"write" operations in one section and "verify"
operation in another section. The --section option only applies to
job sections. The reserved *global* section is always parsed and
used.
- --alloc-size=kb
- Set the internal smalloc pool size to kb in KiB. The
--alloc-size switch allows one to use a larger pool size for
smalloc. If running large jobs with randommap enabled, fio can run out of
memory. Smalloc is an internal allocator for shared structures from a
fixed size memory pool and can grow to 16 pools. The pool size defaults to
16MiB. NOTE: While running `.fio_smalloc.*' backing store files are
visible in `/tmp'.
- --warnings-fatal
- All fio parser warnings are fatal, causing fio to exit with an error.
- --max-jobs=nr
- Set the maximum number of threads/processes to support to nr. NOTE:
On Linux, it may be necessary to increase the shared-memory limit
(`/proc/sys/kernel/shmmax') if fio runs into errors while creating
jobs.
- --server=args
- Start a backend server, with args specifying what to listen to. See
CLIENT/SERVER section.
- --daemonize=pidfile
- Background a fio server, writing the pid to the given pidfile
file.
- --client=hostname
- Instead of running the jobs locally, send and run them on the given
hostname or set of hostnames. See CLIENT/SERVER
section.
- --remote-config=file
- Tell fio server to load this local file.
- --idle-prof=option
- Report CPU idleness. option is one of the following:
- calibrate
- Run unit work calibration only and exit.
- system
- Show aggregate system idleness and unit work.
- percpu
- As system but also show per CPU idleness.
- --inflate-log=log
- Inflate and output compressed log.
- --trigger-file=file
- Execute trigger command when file exists.
- --trigger-timeout=time
- Execute trigger at this time.
- --trigger=command
- Set this command as local trigger.
- --trigger-remote=command
- Set this command as remote trigger.
- --aux-path=path
- Use the directory specified by path for generated state files
instead of the current working directory.
Any parameters following the options will be assumed to be job
files, unless they match a job file parameter. Multiple job files can be
listed and each job file will be regarded as a separate group. Fio will
stonewall execution between each group.
Fio accepts one or more job files describing what it is supposed
to do. The job file format is the classic ini file, where the names enclosed
in [] brackets define the job name. You are free to use any ASCII name you
want, except *global* which has special meaning. Following the job name is a
sequence of zero or more parameters, one per line, that define the behavior
of the job. If the first character in a line is a ';' or a '#', the entire
line is discarded as a comment.
A *global* section sets defaults for the jobs described in that
file. A job may override a *global* section parameter, and a job file may
even have several *global* sections if so desired. A job is only affected by
a *global* section residing above it.
The --cmdhelp option also lists all options. If used with
an command argument, --cmdhelp will detail the given
command.
See the `examples/' directory for inspiration on how to write job
files. Note the copyright and license requirements currently apply to
`examples/' files.
Some parameters take an option of a given type, such as an integer
or a string. Anywhere a numeric value is required, an arithmetic expression
may be used, provided it is surrounded by parentheses. Supported operators
are:
addition (+)
subtraction (-)
multiplication (*)
division (/)
modulus (%)
exponentiation (^)
For time values in expressions, units are microseconds by default.
This is different than for time values not in expressions (not enclosed in
parentheses).
The following parameter types are used.
- str
- String. A sequence of alphanumeric characters.
- time
- Integer with possible time suffix. Without a unit value is interpreted as
seconds unless otherwise specified. Accepts a suffix of 'd' for days, 'h'
for hours, 'm' for minutes, 's' for seconds, 'ms' (or 'msec') for
milliseconds and 'us' (or 'usec') for microseconds. For example, use 10m
for 10 minutes.
- int
- Integer. A whole number value, which may contain an integer prefix and an
integer suffix.
[*integer prefix*] **number** [*integer suffix*]
The optional *integer prefix* specifies the number's base. The
default is decimal. *0x* specifies hexadecimal.
The optional *integer suffix* specifies the number's units, and
includes an optional unit prefix and an optional unit. For quantities of
data, the default unit is bytes. For quantities of time, the default unit is
seconds unless otherwise specified.
With `kb_base=1000', fio follows international standards for unit
prefixes. To specify power-of-10 decimal values defined in the International
System of Units (SI):
K means kilo (K) or 1000
M means mega (M) or 1000**2
G means giga (G) or 1000**3
T means tera (T) or 1000**4
P means peta (P) or 1000**5
To specify power-of-2 binary values defined in IEC 80000-13:
Ki means kibi (Ki) or 1024
Mi means mebi (Mi) or 1024**2
Gi means gibi (Gi) or 1024**3
Ti means tebi (Ti) or 1024**4
Pi means pebi (Pi) or 1024**5
With `kb_base=1024' (the default), the unit prefixes are opposite
from those specified in the SI and IEC 80000-13 standards to provide
compatibility with old scripts. For example, 4k means 4096.
For quantities of data, an optional unit of 'B' may be included
(e.g., 'kB' is the same as 'k').
The *integer suffix* is not case sensitive (e.g., m/mi mean
mebi/mega, not milli). 'b' and 'B' both mean byte, not bit.
Examples with `kb_base=1000':
4 KiB: 4096, 4096b, 4096B, 4k, 4kb, 4kB, 4K, 4KB
1 MiB: 1048576, 1m, 1024k
1 MB: 1000000, 1mi, 1000ki
1 TiB: 1073741824, 1t, 1024m, 1048576k
1 TB: 1000000000, 1ti, 1000mi, 1000000ki
Examples with `kb_base=1024' (default):
4 KiB: 4096, 4096b, 4096B, 4k, 4kb, 4kB, 4K, 4KB
1 MiB: 1048576, 1m, 1024k
1 MB: 1000000, 1mi, 1000ki
1 TiB: 1073741824, 1t, 1024m, 1048576k
1 TB: 1000000000, 1ti, 1000mi, 1000000ki
To specify times (units are not case sensitive):
D means days
H means hours
M mean minutes
s or sec means seconds (default)
ms or msec means milliseconds
us or usec means microseconds
If the option accepts an upper and lower range, use a colon ':' or
minus '-' to separate such values. See irange parameter type. If the
lower value specified happens to be larger than the upper value the two
values are swapped.
- bool
- Boolean. Usually parsed as an integer, however only defined for true and
false (1 and 0).
- irange
- Integer range with suffix. Allows value range to be given, such as
1024-4096. A colon may also be used as the separator, e.g. 1k:4k. If the
option allows two sets of ranges, they can be specified with a ',' or '/'
delimiter: 1k-4k/8k-32k. Also see int parameter type.
- float_list
- A list of floating point numbers, separated by a ':' character.
With the above in mind, here follows the complete list of fio job
parameters.
- kb_base=int
- Select the interpretation of unit prefixes in input parameters.
- 1000
- Inputs comply with IEC 80000-13 and the International System of Units
(SI). Use:
- power-of-2 values with IEC prefixes (e.g., KiB)
- power-of-10 values with SI prefixes (e.g., kB)
- 1024
- Compatibility mode (default). To avoid breaking old scripts:
- power-of-2 values with SI prefixes
- power-of-10 values with IEC prefixes
See bs for more details on input parameters.
Outputs always use correct prefixes. Most outputs include both
side-by-side, like:
bw=2383.3kB/s (2327.4KiB/s)
If only one value is reported, then kb_base selects the one to
use:
1000 -- SI prefixes
1024 -- IEC prefixes
- unit_base=int
- Base unit for reporting. Allowed values are:
- 0
- Use auto-detection (default).
- 8
- Byte based.
- 1
- Bit based.
- name=str
- ASCII name of the job. This may be used to override the name printed by
fio for this job. Otherwise the job name is used. On the command line this
parameter has the special purpose of also signaling the start of a new
job.
- description=str
- Text description of the job. Doesn't do anything except dump this text
description when this job is run. It's not parsed.
- loops=int
- Run the specified number of iterations of this job. Used to repeat the
same workload a given number of times. Defaults to 1.
- numjobs=int
- Create the specified number of clones of this job. Each clone of job is
spawned as an independent thread or process. May be used to setup a larger
number of threads/processes doing the same thing. Each thread is reported
separately; to see statistics for all clones as a whole, use
group_reporting in conjunction with new_group. See
--max-jobs. Default: 1.
- runtime=time
- Tell fio to terminate processing after the specified period of time. It
can be quite hard to determine for how long a specified job will run, so
this parameter is handy to cap the total runtime to a given time. When the
unit is omitted, the value is interpreted in seconds.
- time_based
- If set, fio will run for the duration of the runtime specified even
if the file(s) are completely read or written. It will simply loop over
the same workload as many times as the runtime allows.
- startdelay=irange(int)
- Delay the start of job for the specified amount of time. Can be a single
value or a range. When given as a range, each thread will choose a value
randomly from within the range. Value is in seconds if a unit is
omitted.
- ramp_time=time
- If set, fio will run the specified workload for this amount of time before
logging any performance numbers. Useful for letting performance settle
before logging results, thus minimizing the runtime required for stable
results. Note that the ramp_time is considered lead in time for a
job, thus it will increase the total runtime if a special timeout or
runtime is specified. When the unit is omitted, the value is given
in seconds.
- clocksource=str
- Use the given clocksource as the base of timing. The supported options
are:
cpu is the preferred clocksource if it is reliable, as it
is very fast (and fio is heavy on time calls). Fio will automatically use
this clocksource if it's supported and considered reliable on the system it
is running on, unless another clocksource is specifically set. For
x86/x86-64 CPUs, this means supporting TSC Invariant.
- gtod_reduce=bool
- Enable all of the gettimeofday(2) reducing options
(disable_clat, disable_slat, disable_bw_measurement)
plus reduce precision of the timeout somewhat to really shrink the
gettimeofday(2) call count. With this option enabled, we only do
about 0.4% of the gettimeofday(2) calls we would have done if all
time keeping was enabled.
- gtod_cpu=int
- Sometimes it's cheaper to dedicate a single thread of execution to just
getting the current time. Fio (and databases, for instance) are very
intensive on gettimeofday(2) calls. With this option, you can set
one CPU aside for doing nothing but logging current time to a shared
memory location. Then the other threads/processes that run I/O workloads
need only copy that segment, instead of entering the kernel with a
gettimeofday(2) call. The CPU set aside for doing these time calls
will be excluded from other uses. Fio will manually clear it from the CPU
mask of other jobs.
- directory=str
- Prefix filenames with this directory. Used to place files in a
different location than `./'. You can specify a number of directories by
separating the names with a ':' character. These directories will be
assigned equally distributed to job clones created by numjobs as
long as they are using generated filenames. If specific filename(s)
are set fio will use the first listed directory, and thereby matching the
filename semantic (which generates a file for each clone if not
specified, but lets all clones use the same file if set).
See the filename option for information on how to escape
':' and '\' characters within the directory path itself.
Note: To control the directory fio will use for internal state
files use --aux-path.
- filename=str
- Fio normally makes up a filename based on the job name, thread
number, and file number (see filename_format). If you want to share
files between threads in a job or several jobs with fixed file paths,
specify a filename for each of them to override the default. If the
ioengine is file based, you can specify a number of files by separating
the names with a ':' colon. So if you wanted a job to open `/dev/sda' and
`/dev/sdb' as the two working files, you would use
`filename=/dev/sda:/dev/sdb'. This also means that whenever this option is
specified, nrfiles is ignored. The size of regular files specified
by this option will be size divided by number of files unless an
explicit size is specified by filesize.
Each colon and backslash in the wanted path must be escaped with a
'\' character. For instance, if the path is `/dev/dsk/foo@3,0:c' then you
would use `filename=/dev/dsk/foo@3,0\:c' and if the path is `F:\filename'
then you would use `filename=F\:\\filename'.
On Windows, disk devices are accessed as `\\.\PhysicalDrive0' for
the first device, `\\.\PhysicalDrive1' for the second etc. Note: Windows and
FreeBSD prevent write access to areas of the disk containing in-use data
(e.g. filesystems).
The filename `-' is a reserved name, meaning *stdin* or *stdout*.
Which of the two depends on the read/write direction set.
- filename_format=str
- If sharing multiple files between jobs, it is usually necessary to have
fio generate the exact names that you want. By default, fio will name a
file based on the default file format specification of
`jobname.jobnumber.filenumber'. With this option, that can be customized.
Fio will recognize and replace the following keywords in this string:
- $jobname
- The name of the worker thread or process.
- $jobnum
- The incremental number of the worker thread or process.
- $filenum
- The incremental number of the file for that worker thread or process.
To have dependent jobs share a set of files, this option can be
set to have fio generate filenames that are shared between the two. For
instance, if `testfiles.$filenum' is specified, file number 4 for any job
will be named `testfiles.4'. The default of `$jobname.$jobnum.$filenum' will
be used if no other format specifier is given.
If you specify a path then the directories will be created up to
the main directory for the file. So for example if you specify
`a/b/c/$jobnum` then the directories a/b/c will be created before the file
setup part of the job. If you specify directory then the path will be
relative that directory, otherwise it is treated as the absolute path.
- unique_filename=bool
- To avoid collisions between networked clients, fio defaults to prefixing
any generated filenames (with a directory specified) with the source of
the client connecting. To disable this behavior, set this option to
0.
- opendir=str
- Recursively open any files below directory str.
- lockfile=str
- Fio defaults to not locking any files before it does I/O to them. If a
file or file descriptor is shared, fio can serialize I/O to that file to
make the end result consistent. This is usual for emulating real workloads
that share files. The lock modes are:
- none
- No locking. The default.
- exclusive
- Only one thread or process may do I/O at a time, excluding all
others.
- readwrite
- Read-write locking on the file. Many readers may access the file at the
same time, but writes get exclusive access.
- nrfiles=int
- Number of files to use for this job. Defaults to 1. The size of files will
be size divided by this unless explicit size is specified by
filesize. Files are created for each thread separately, and each
file will have a file number within its name by default, as explained in
filename section.
- openfiles=int
- Number of files to keep open at the same time. Defaults to the same as
nrfiles, can be set smaller to limit the number simultaneous
opens.
- file_service_type=str
- Defines how fio decides which file from a job to service next. The
following types are defined:
- random
- Choose a file at random.
- roundrobin
- Round robin over opened files. This is the default.
- sequential
- Finish one file before moving on to the next. Multiple files can still be
open depending on openfiles.
- zipf
- Use a Zipf distribution to decide what file to access.
- pareto
- Use a Pareto distribution to decide what file to access.
- normal
- Use a Gaussian (normal) distribution to decide what file to access.
- gauss
- Alias for normal.
For random, roundrobin, and sequential, a
postfix can be appended to tell fio how many I/Os to issue before switching
to a new file. For example, specifying `file_service_type=random:8' would
cause fio to issue 8 I/Os before selecting a new file at random. For the
non-uniform distributions, a floating point postfix can be given to
influence how the distribution is skewed. See random_distribution for
a description of how that would work.
- ioscheduler=str
- Attempt to switch the device hosting the file to the specified I/O
scheduler before running.
- create_serialize=bool
- If true, serialize the file creation for the jobs. This may be handy to
avoid interleaving of data files, which may greatly depend on the
filesystem used and even the number of processors in the system. Default:
true.
- create_fsync=bool
- fsync(2) the data file after creation. This is the default.
- create_on_open=bool
- If true, don't pre-create files but allow the job's open() to create a
file when it's time to do I/O. Default: false -- pre-create all necessary
files when the job starts.
- create_only=bool
- If true, fio will only run the setup phase of the job. If files need to be
laid out or updated on disk, only that will be done -- the actual job
contents are not executed. Default: false.
- allow_file_create=bool
- If true, fio is permitted to create files as part of its workload. If this
option is false, then fio will error out if the files it needs to use
don't already exist. Default: true.
- allow_mounted_write=bool
- If this isn't set, fio will abort jobs that are destructive (e.g. that
write) to what appears to be a mounted device or partition. This should
help catch creating inadvertently destructive tests, not realizing that
the test will destroy data on the mounted file system. Note that some
platforms don't allow writing against a mounted device regardless of this
option. Default: false.
- pre_read=bool
- If this is given, files will be pre-read into memory before starting the
given I/O operation. This will also clear the invalidate flag,
since it is pointless to pre-read and then drop the cache. This will only
work for I/O engines that are seek-able, since they allow you to read the
same data multiple times. Thus it will not work on non-seekable I/O
engines (e.g. network, splice). Default: false.
- unlink=bool
- Unlink the job files when done. Not the default, as repeated runs of that
job would then waste time recreating the file set again and again.
Default: false.
- unlink_each_loop=bool
- Unlink job files after each iteration or loop. Default: false.
- zonemode=str
- Accepted values are:
- none
- The zonerange, zonesize and zoneskip parameters are
ignored.
- strided
- I/O happens in a single zone until zonesize bytes have been
transferred. After that number of bytes has been transferred processing of
the next zone starts.
- zbd
- Zoned block device mode. I/O happens sequentially in each zone, even if
random I/O has been selected. Random I/O happens across all zones instead
of being restricted to a single zone.
- zonerange=int
- Size of a single zone. See also zonesize and zoneskip.
- zonesize=int
- For zonemode=strided, this is the number of bytes to transfer
before skipping zoneskip bytes. If this parameter is smaller than
zonerange then only a fraction of each zone with zonerange
bytes will be accessed. If this parameter is larger than zonerange
then each zone will be accessed multiple times before skipping to the next
zone.
For zonemode=zbd, this is the size of a single zone.
The zonerange parameter is ignored in this mode.
- zoneskip=int
- For zonemode=strided, the number of bytes to skip after
zonesize bytes of data have been transferred. This parameter must
be zero for zonemode=zbd.
- read_beyond_wp=bool
- This parameter applies to zonemode=zbd only.
Zoned block devices are block devices that consist of multiple
zones. Each zone has a type, e.g. conventional or sequential. A
conventional zone can be written at any offset that is a multiple of the
block size. Sequential zones must be written sequentially. The position
at which a write must occur is called the write pointer. A zoned block
device can be either drive managed, host managed or host aware. For host
managed devices the host must ensure that writes happen sequentially.
Fio recognizes host managed devices and serializes writes to sequential
zones for these devices.
If a read occurs in a sequential zone beyond the write pointer
then the zoned block device will complete the read without reading any
data from the storage medium. Since such reads lead to unrealistically
high bandwidth and IOPS numbers fio only reads beyond the write pointer
if explicitly told to do so. Default: false.
- max_open_zones=int
- When running a random write test across an entire drive many more zones
will be open than in a typical application workload. Hence this command
line option that allows to limit the number of open zones. The number of
open zones is defined as the number of zones to which write commands are
issued.
- zone_reset_threshold=float
- A number between zero and one that indicates the ratio of logical blocks
with data to the total number of logical blocks in the test above which
zones should be reset periodically.
- zone_reset_frequency=float
- A number between zero and one that indicates how often a zone reset should
be issued if the zone reset threshold has been exceeded. A zone reset is
submitted after each (1 / zone_reset_frequency) write requests. This and
the previous parameter can be used to simulate garbage collection
activity.
- direct=bool
- If value is true, use non-buffered I/O. This is usually O_DIRECT. Note
that OpenBSD and ZFS on Solaris don't support direct I/O. On Windows the
synchronous ioengines don't support direct I/O. Default: false.
- atomic=bool
- If value is true, attempt to use atomic direct I/O. Atomic writes are
guaranteed to be stable once acknowledged by the operating system. Only
Linux supports O_ATOMIC right now.
- buffered=bool
- If value is true, use buffered I/O. This is the opposite of the
direct option. Defaults to true.
- readwrite=str,
rw=str
- Type of I/O pattern. Accepted values are:
- read
- Sequential reads.
- write
- Sequential writes.
- trim
- Sequential trims (Linux block devices and SCSI character devices
only).
- randread
- Random reads.
- randwrite
- Random writes.
- randtrim
- Random trims (Linux block devices and SCSI character devices only).
- rw,readwrite
- Sequential mixed reads and writes.
- randrw
- Random mixed reads and writes.
- trimwrite
- Sequential trim+write sequences. Blocks will be trimmed first, then the
same blocks will be written to.
Fio defaults to read if the option is not specified. For the mixed
I/O types, the default is to split them 50/50. For certain types of I/O the
result may still be skewed a bit, since the speed may be different.
It is possible to specify the number of I/Os to do before getting
a new offset by appending `:<nr>' to the end of the string given. For
a random read, it would look like `rw=randread:8' for passing in an offset
modifier with a value of 8. If the suffix is used with a sequential I/O
pattern, then the `<nr>' value specified will be added to the
generated offset for each I/O turning sequential I/O into sequential I/O
with holes. For instance, using `rw=write:4k' will skip 4k for every write.
Also see the rw_sequencer option.
- rw_sequencer=str
- If an offset modifier is given by appending a number to the
`rw=str' line, then this option controls how that number modifies
the I/O offset being generated. Accepted values are:
sequential is only useful for random I/O, where fio would
normally generate a new random offset for every I/O. If you append e.g. 8 to
randread, you would get a new random offset for every 8 I/Os. The result
would be a seek for only every 8 I/Os, instead of for every I/O. Use
`rw=randread:8' to specify that. As sequential I/O is already sequential,
setting sequential for that would not result in any differences.
identical behaves in a similar fashion, except it sends the same
offset 8 number of times before generating a new offset.
- unified_rw_reporting=bool
- Fio normally reports statistics on a per data direction basis, meaning
that reads, writes, and trims are accounted and reported separately. If
this option is set fio sums the results and report them as
"mixed" instead.
- randrepeat=bool
- Seed the random number generator used for random I/O patterns in a
predictable way so the pattern is repeatable across runs. Default:
true.
- allrandrepeat=bool
- Seed all random number generators in a predictable way so results are
repeatable across runs. Default: false.
- randseed=int
- Seed the random number generators based on this seed value, to be able to
control what sequence of output is being generated. If not set, the random
sequence depends on the randrepeat setting.
- fallocate=str
- Whether pre-allocation is performed when laying down files. Accepted
values are:
- none
- Do not pre-allocate space.
- native
- Use a platform's native pre-allocation call but fall back to none
behavior if it fails/is not implemented.
- posix
- Pre-allocate via posix_fallocate(3).
- keep
- Pre-allocate via fallocate(2) with FALLOC_FL_KEEP_SIZE set.
- 0
- Backward-compatible alias for none.
- 1
- Backward-compatible alias for posix.
May not be available on all supported platforms. keep is
only available on Linux. If using ZFS on Solaris this cannot be set to
posix because ZFS doesn't support pre-allocation. Default:
native if any pre-allocation methods are available, none if
not.
- fadvise_hint=str
- Use posix_fadvise(2) or posix_madvise(2) to advise the
kernel what I/O patterns are likely to be issued. Accepted values
are:
- 0
- Backwards compatible hint for "no hint".
- 1
- Backwards compatible hint for "advise with fio workload type".
This uses FADV_RANDOM for a random workload, and FADV_SEQUENTIAL for a
sequential workload.
- sequential
- Advise using FADV_SEQUENTIAL.
- random
- Advise using FADV_RANDOM.
- write_hint=str
- Use fcntl(2) to advise the kernel what life time to expect from a
write. Only supported on Linux, as of version 4.13. Accepted values
are:
- none
- No particular life time associated with this file.
- short
- Data written to this file has a short life time.
- medium
- Data written to this file has a medium life time.
- long
- Data written to this file has a long life time.
- extreme
- Data written to this file has a very long life time.
The values are all relative to each other, and no absolute meaning
should be associated with them.
- offset=int
- Start I/O at the provided offset in the file, given as either a fixed size
in bytes or a percentage. If a percentage is given, the generated offset
will be aligned to the minimum blocksize or to the value of
offset_align if provided. Data before the given offset will not be
touched. This effectively caps the file size at `real_size - offset'. Can
be combined with size to constrain the start and end range of the
I/O workload. A percentage can be specified by a number between 1 and 100
followed by '%', for example, `offset=20%' to specify 20%.
- offset_align=int
- If set to non-zero value, the byte offset generated by a percentage
offset is aligned upwards to this value. Defaults to 0 meaning that
a percentage offset is aligned to the minimum block size.
- offset_increment=int
- If this is provided, then the real offset becomes `offset +
offset_increment * thread_number', where the thread number is a
counter that starts at 0 and is incremented for each sub-job (i.e. when
numjobs option is specified). This option is useful if there are
several jobs which are intended to operate on a file in parallel disjoint
segments, with even spacing between the starting points.
- number_ios=int
- Fio will normally perform I/Os until it has exhausted the size of the
region set by size, or if it exhaust the allocated time (or hits an
error condition). With this setting, the range/size can be set
independently of the number of I/Os to perform. When fio reaches this
number, it will exit normally and report status. Note that this does not
extend the amount of I/O that will be done, it will only stop fio if this
condition is met before other end-of-job criteria.
- fsync=int
- If writing to a file, issue an fsync(2) (or its equivalent) of the
dirty data for every number of blocks given. For example, if you give 32
as a parameter, fio will sync the file after every 32 writes issued. If
fio is using non-buffered I/O, we may not sync the file. The exception is
the sg I/O engine, which synchronizes the disk cache anyway. Defaults to
0, which means fio does not periodically issue and wait for a sync to
complete. Also see end_fsync and fsync_on_close.
- fdatasync=int
- Like fsync but uses fdatasync(2) to only sync data and not
metadata blocks. In Windows, FreeBSD, and DragonFlyBSD there is no
fdatasync(2) so this falls back to using fsync(2). Defaults
to 0, which means fio does not periodically issue and wait for a data-only
sync to complete.
- write_barrier=int
- Make every N-th write a barrier write.
- sync_file_range=str:int
- Use sync_file_range(2) for every int number of write
operations. Fio will track range of writes that have happened since the
last sync_file_range(2) call. str can currently be one or
more of:
So if you do `sync_file_range=wait_before,write:8', fio would use
`SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE' for every 8 writes.
Also see the sync_file_range(2) man page. This option is Linux
specific.
- overwrite=bool
- If true, writes to a file will always overwrite existing data. If the file
doesn't already exist, it will be created before the write phase begins.
If the file exists and is large enough for the specified write phase,
nothing will be done. Default: false.
- end_fsync=bool
- If true, fsync(2) file contents when a write stage has completed.
Default: false.
- fsync_on_close=bool
- If true, fio will fsync(2) a dirty file on close. This differs from
end_fsync in that it will happen on every file close, not just at
the end of the job. Default: false.
- rwmixread=int
- Percentage of a mixed workload that should be reads. Default: 50.
- rwmixwrite=int
- Percentage of a mixed workload that should be writes. If both
rwmixread and rwmixwrite is given and the values do not add
up to 100%, the latter of the two will be used to override the first. This
may interfere with a given rate setting, if fio is asked to limit reads or
writes to a certain rate. If that is the case, then the distribution may
be skewed. Default: 50.
- random_distribution=str:float[,str:float][,str:float]
- By default, fio will use a completely uniform random distribution when
asked to perform random I/O. Sometimes it is useful to skew the
distribution in specific ways, ensuring that some parts of the data is
more hot than others. fio includes the following distribution models:
- random
- Uniform random distribution
- zipf
- Zipf distribution
- pareto
- Pareto distribution
- normal
- Normal (Gaussian) distribution
- zoned
- Zoned random distribution zoned_abs Zoned absolute random
distribution
When using a zipf or pareto distribution, an input
value is also needed to define the access pattern. For zipf, this is
the `Zipf theta'. For pareto, it's the `Pareto power'. Fio includes a
test program, fio-genzipf, that can be used visualize what the given
input values will yield in terms of hit rates. If you wanted to use
zipf with a `theta' of 1.2, you would use
`random_distribution=zipf:1.2' as the option. If a non-uniform model is
used, fio will disable use of the random map. For the normal
distribution, a normal (Gaussian) deviation is supplied as a value between 0
and 100.
For a zoned distribution, fio supports specifying
percentages of I/O access that should fall within what range of the file or
device. For example, given a criteria of:
60% of accesses should be to the first 10%
30% of accesses should be to the next 20%
8% of accesses should be to the next 30%
2% of accesses should be to the next 40%
we can define that through zoning of the random accesses. For the
above example, the user would do:
random_distribution=zoned:60/10:30/20:8/30:2/40
A zoned_abs distribution works exactly like
thezoned, except that it takes absolute sizes. For example, let's say
you wanted to define access according to the following criteria:
60% of accesses should be to the first 20G
30% of accesses should be to the next 100G
10% of accesses should be to the next 500G
we can define an absolute zoning distribution with:
random_distribution=zoned:60/10:30/20:8/30:2/40
For both zoned and zoned_abs, fio supports defining
up to 256 separate zones.
Similarly to how bssplit works for setting ranges and
percentages of block sizes. Like bssplit, it's possible to specify
separate zones for reads, writes, and trims. If just one set is given, it'll
apply to all of them.
- percentage_random=int[,int][,int]
- For a random workload, set how big a percentage should be random. This
defaults to 100%, in which case the workload is fully random. It can be
set from anywhere from 0 to 100. Setting it to 0 would make the workload
fully sequential. Any setting in between will result in a random mix of
sequential and random I/O, at the given percentages. Comma-separated
values may be specified for reads, writes, and trims as described in
blocksize.
- norandommap
- Normally fio will cover every block of the file when doing random I/O. If
this option is given, fio will just get a new random offset without
looking at past I/O history. This means that some blocks may not be read
or written, and that some blocks may be read/written more than once. If
this option is used with verify and multiple blocksizes (via
bsrange), only intact blocks are verified, i.e.,
partially-overwritten blocks are ignored. With an async I/O engine and an
I/O depth > 1, it is possible for the same block to be overwritten,
which can cause verification errors. Either do not use norandommap in this
case, or also use the lfsr random generator.
- softrandommap=bool
- See norandommap. If fio runs with the random block map enabled and
it fails to allocate the map, if this option is set it will continue
without a random block map. As coverage will not be as complete as with
random maps, this option is disabled by default.
- random_generator=str
- Fio supports the following engines for generating I/O offsets for random
I/O:
- tausworthe
- Strong 2^88 cycle random number generator.
- lfsr
- Linear feedback shift register generator.
- tausworthe64
- Strong 64-bit 2^258 cycle random number generator.
tausworthe is a strong random number generator, but it
requires tracking on the side if we want to ensure that blocks are only read
or written once. lfsr guarantees that we never generate the same
offset twice, and it's also less computationally expensive. It's not a true
random generator, however, though for I/O purposes it's typically good
enough. lfsr only works with single block sizes, not with workloads
that use multiple block sizes. If used with such a workload, fio may read or
write some blocks multiple times. The default value is tausworthe,
unless the required space exceeds 2^32 blocks. If it does, then
tausworthe64 is selected automatically.
- blocksize=int[,int][,int],
bs=int[,int][,int]
- The block size in bytes used for I/O units. Default: 4096. A single value
applies to reads, writes, and trims. Comma-separated values may be
specified for reads, writes, and trims. A value not terminated in a comma
applies to subsequent types. Examples:
bs=256k means 256k for reads, writes and trims.
bs=8k,32k means 8k for reads, 32k for writes and trims.
bs=8k,32k, means 8k for reads, 32k for writes, and default for
trims.
bs=,8k means default for reads, 8k for writes and trims.
bs=,8k, means default for reads, 8k for writes, and default for
trims.
- blocksize_range=irange[,irange][,irange],
bsrange=irange[,irange][,irange]
- A range of block sizes in bytes for I/O units. The issued I/O unit will
always be a multiple of the minimum size, unless
blocksize_unaligned is set. Comma-separated ranges may be specified
for reads, writes, and trims as described in blocksize.
Example:
- bssplit=str[,str][,str]
- Sometimes you want even finer grained control of the block sizes issued,
not just an even split between them. This option allows you to weight
various block sizes, so that you are able to define a specific amount of
block sizes issued. The format for this option is:
bssplit=blocksize/percentage:blocksize/percentage
for as many block sizes as needed. So if you want to define a
workload that has 50% 64k blocks, 10% 4k blocks, and 40% 32k blocks, you
would write:
bssplit=4k/10:64k/50:32k/40
Ordering does not matter. If the percentage is left blank, fio
will fill in the remaining values evenly. So a bssplit option like this
one:
would have 50% 4k ios, and 25% 1k and 32k ios. The percentages
always add up to 100, if bssplit is given a range that adds up to more, it
will error out.
Comma-separated values may be specified for reads, writes, and
trims as described in blocksize.
If you want a workload that has 50% 2k reads and 50% 4k reads,
while having 90% 4k writes and 10% 8k writes, you would specify:
bssplit=2k/50:4k/50,4k/90:8k/10
Fio supports defining up to 64 different weights for each data
direction.
- blocksize_unaligned,
bs_unaligned
- If set, fio will issue I/O units with any size within
blocksize_range, not just multiples of the minimum size. This
typically won't work with direct I/O, as that normally requires sector
alignment.
- bs_is_seq_rand=bool
- If this option is set, fio will use the normal read,write blocksize
settings as sequential,random blocksize settings instead. Any random read
or write will use the WRITE blocksize settings, and any sequential read or
write will use the READ blocksize settings.
- blockalign=int[,int][,int],
ba=int[,int][,int]
- Boundary to which fio will align random I/O units. Default:
blocksize. Minimum alignment is typically 512b for using direct
I/O, though it usually depends on the hardware block size. This option is
mutually exclusive with using a random map for files, so it will turn off
that option. Comma-separated values may be specified for reads, writes,
and trims as described in blocksize.
- zero_buffers
- Initialize buffers with all zeros. Default: fill buffers with random
data.
- refill_buffers
- If this option is given, fio will refill the I/O buffers on every submit.
The default is to only fill it at init time and reuse that data. Only
makes sense if zero_buffers isn't specified, naturally. If data
verification is enabled, refill_buffers is also automatically
enabled.
- scramble_buffers=bool
- If refill_buffers is too costly and the target is using data
deduplication, then setting this option will slightly modify the I/O
buffer contents to defeat normal de-dupe attempts. This is not enough to
defeat more clever block compression attempts, but it will stop naive
dedupe of blocks. Default: true.
- buffer_compress_percentage=int
- If this is set, then fio will attempt to provide I/O buffer content (on
WRITEs) that compresses to the specified level. Fio does this by providing
a mix of random data followed by fixed pattern data. The fixed pattern is
either zeros, or the pattern specified by buffer_pattern. If the
buffer_pattern option is used, it might skew the compression ratio
slightly. Setting buffer_compress_percentage to a value other than
100 will also enable refill_buffers in order to reduce the
likelihood that adjacent blocks are so similar that they over compress
when seen together. See buffer_compress_chunk for how to set a
finer or coarser granularity of the random/fixed data regions. Defaults to
unset i.e., buffer data will not adhere to any compression level.
- buffer_compress_chunk=int
- This setting allows fio to manage how big the random/fixed data region is
when using buffer_compress_percentage. When
buffer_compress_chunk is set to some non-zero value smaller than
the block size, fio can repeat the random/fixed region throughout the I/O
buffer at the specified interval (which particularly useful when bigger
block sizes are used for a job). When set to 0, fio will use a chunk size
that matches the block size resulting in a single random/fixed region
within the I/O buffer. Defaults to 512. When the unit is omitted, the
value is interpreted in bytes.
- buffer_pattern=str
- If set, fio will fill the I/O buffers with this pattern or with the
contents of a file. If not set, the contents of I/O buffers are defined by
the other options related to buffer contents. The setting can be any
pattern of bytes, and can be prefixed with 0x for hex values. It may also
be a string, where the string must then be wrapped with "". Or
it may also be a filename, where the filename must be wrapped with '' in
which case the file is opened and read. Note that not all the file
contents will be read if that would cause the buffers to overflow. So, for
example:
buffer_pattern='filename'
or:
buffer_pattern="abcd"
or:
buffer_pattern=-12
or:
buffer_pattern=0xdeadface
Also you can combine everything together in any order:
buffer_pattern=0xdeadface"abcd"-12'filename'
- dedupe_percentage=int
- If set, fio will generate this percentage of identical buffers when
writing. These buffers will be naturally dedupable. The contents of the
buffers depend on what other buffer compression settings have been set.
It's possible to have the individual buffers either fully compressible, or
not at all -- this option only controls the distribution of unique
buffers. Setting this option will also enable refill_buffers to
prevent every buffer being identical.
- invalidate=bool
- Invalidate the buffer/page cache parts of the files to be used prior to
starting I/O if the platform and file type support it. Defaults to true.
This will be ignored if pre_read is also specified for the same
job.
- sync=bool
- Use synchronous I/O for buffered writes. For the majority of I/O engines,
this means using O_SYNC. Default: false.
- iomem=str,
mem=str
- Fio can use various types of memory as the I/O unit buffer. The allowed
values are:
- malloc
- Use memory from malloc(3) as the buffers. Default memory type.
- shm
- Use shared memory as the buffers. Allocated through shmget(2).
- shmhuge
- Same as shm, but use huge pages as backing.
- mmap
- Use mmap(2) to allocate buffers. May either be anonymous memory, or
can be file backed if a filename is given after the option. The format is
`mem=mmap:/path/to/file'.
- mmaphuge
- Use a memory mapped huge file as the buffer backing. Append filename after
mmaphuge, ala `mem=mmaphuge:/hugetlbfs/file'.
- mmapshared
- Same as mmap, but use a MMAP_SHARED mapping.
- cudamalloc
- Use GPU memory as the buffers for GPUDirect RDMA benchmark. The
ioengine must be rdma.
The area allocated is a function of the maximum allowed bs size
for the job, multiplied by the I/O depth given. Note that for shmhuge
and mmaphuge to work, the system must have free huge pages allocated.
This can normally be checked and set by reading/writing
`/proc/sys/vm/nr_hugepages' on a Linux system. Fio assumes a huge page is
4MiB in size. So to calculate the number of huge pages you need for a given
job file, add up the I/O depth of all jobs (normally one unless
iodepth is used) and multiply by the maximum bs set. Then divide that
number by the huge page size. You can see the size of the huge pages in
`/proc/meminfo'. If no huge pages are allocated by having a non-zero number
in `nr_hugepages', using mmaphuge or shmhuge will fail. Also
see hugepage-size.
mmaphuge also needs to have hugetlbfs mounted and the file
location should point there. So if it's mounted in `/huge', you would use
`mem=mmaphuge:/huge/somefile'.
- iomem_align=int,
mem_align=int
- This indicates the memory alignment of the I/O memory buffers. Note that
the given alignment is applied to the first I/O unit buffer, if using
iodepth the alignment of the following buffers are given by the
bs used. In other words, if using a bs that is a multiple of
the page sized in the system, all buffers will be aligned to this value.
If using a bs that is not page aligned, the alignment of subsequent
I/O memory buffers is the sum of the iomem_align and bs
used.
- hugepage-size=int
- Defines the size of a huge page. Must at least be equal to the system
setting, see `/proc/meminfo'. Defaults to 4MiB. Should probably always be
a multiple of megabytes, so using `hugepage-size=Xm' is the preferred way
to set this to avoid setting a non-pow-2 bad value.
- lockmem=int
- Pin the specified amount of memory with mlock(2). Can be used to
simulate a smaller amount of memory. The amount specified is per
worker.
- size=int
- The total size of file I/O for each thread of this job. Fio will run until
this many bytes has been transferred, unless runtime is limited by other
options (such as runtime, for instance, or increased/decreased by
io_size). Fio will divide this size between the available files
determined by options such as nrfiles, filename, unless
filesize is specified by the job. If the result of division happens
to be 0, the size is set to the physical size of the given files or
devices if they exist. If this option is not specified, fio will use the
full size of the given files or devices. If the files do not exist, size
must be given. It is also possible to give size as a percentage between 1
and 100. If `size=20%' is given, fio will use 20% of the full size of the
given files or devices. Can be combined with offset to constrain
the start and end range that I/O will be done within.
- io_size=int,
io_limit=int
- Normally fio operates within the region set by size, which means
that the size option sets both the region and size of I/O to be
performed. Sometimes that is not what you want. With this option, it is
possible to define just the amount of I/O that fio should do. For
instance, if size is set to 20GiB and io_size is set to
5GiB, fio will perform I/O within the first 20GiB but exit when 5GiB have
been done. The opposite is also possible -- if size is set to
20GiB, and io_size is set to 40GiB, then fio will do 40GiB of I/O
within the 0..20GiB region.
- filesize=irange(int)
- Individual file sizes. May be a range, in which case fio will select sizes
for files at random within the given range and limited to size in
total (if that is given). If not given, each created file is the same
size. This option overrides size in terms of file size, which means
this value is used as a fixed size or possible range of each file.
- file_append=bool
- Perform I/O after the end of the file. Normally fio will operate within
the size of a file. If this option is set, then fio will append to the
file instead. This has identical behavior to setting offset to the
size of a file. This option is ignored on non-regular files.
- fill_device=bool,
fill_fs=bool
- Sets size to something really large and waits for ENOSPC (no space left on
device) as the terminating condition. Only makes sense with sequential
write. For a read workload, the mount point will be filled first then I/O
started on the result. This option doesn't make sense if operating on a
raw device node, since the size of that is already known by the file
system. Additionally, writing beyond end-of-device will not return ENOSPC
there.
- ioengine=str
- Defines how the job issues I/O to the file. The following types are
defined:
- sync
- Basic read(2) or write(2) I/O. lseek(2) is used to
position the I/O location. See fsync and fdatasync for
syncing write I/Os.
- psync
- Basic pread(2) or pwrite(2) I/O. Default on all supported
operating systems except for Windows.
- vsync
- Basic readv(2) or writev(2) I/O. Will emulate queuing by
coalescing adjacent I/Os into a single submission.
- pvsync
- Basic preadv(2) or pwritev(2) I/O.
- pvsync2
- Basic preadv2(2) or pwritev2(2) I/O.
- libaio
- Linux native asynchronous I/O. Note that Linux may only support queued
behavior with non-buffered I/O (set `direct=1' or `buffered=0'). This
engine defines engine specific options.
- posixaio
- POSIX asynchronous I/O using aio_read(3) and
aio_write(3).
- solarisaio
- Solaris native asynchronous I/O.
- windowsaio
- Windows native asynchronous I/O. Default on Windows.
- mmap
- File is memory mapped with mmap(2) and data copied to/from using
memcpy(3).
- splice
- splice(2) is used to transfer the data and vmsplice(2) to
transfer data from user space to the kernel.
- sg
- SCSI generic sg v3 I/O. May either be synchronous using the SG_IO ioctl,
or if the target is an sg character device we use read(2) and
write(2) for asynchronous I/O. Requires filename option to
specify either block or character devices. This engine supports trim
operations. The sg engine includes engine specific options.
- null
- Doesn't transfer any data, just pretends to. This is mainly used to
exercise fio itself and for debugging/testing purposes.
- net
- Transfer over the network to given `host:port'. Depending on the
protocol used, the hostname, port, listen and
filename options are used to specify what sort of connection to
make, while the protocol option determines which protocol will be
used. This engine defines engine specific options.
- netsplice
- Like net, but uses splice(2) and vmsplice(2) to map
data and send/receive. This engine defines engine specific options.
- cpuio
- Doesn't transfer any data, but burns CPU cycles according to the
cpuload and cpuchunks options. Setting cpuload=85
will cause that job to do nothing but burn 85% of the CPU. In case of SMP
machines, use `numjobs=<nr_of_cpu>' to get desired CPU usage, as the
cpuload only loads a single CPU at the desired rate. A job never finishes
unless there is at least one non-cpuio job.
- guasi
- The GUASI I/O engine is the Generic Userspace Asynchronous Syscall
Interface approach to async I/O. See
http://www.xmailserver.org/guasi-lib.html for more info on
GUASI.
- rdma
- The RDMA I/O engine supports both RDMA memory semantics
(RDMA_WRITE/RDMA_READ) and channel semantics (Send/Recv) for the
InfiniBand, RoCE and iWARP protocols. This engine defines engine specific
options.
- falloc
- I/O engine that does regular fallocate to simulate data transfer as fio
ioengine.
DDIR_READ does fallocate(,mode = FALLOC_FL_KEEP_SIZE,).
DIR_WRITE does fallocate(,mode = 0).
DDIR_TRIM does fallocate(,mode =
FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE).
- ftruncate
- I/O engine that sends ftruncate(2) operations in response to write
(DDIR_WRITE) events. Each ftruncate issued sets the file's size to the
current block offset. blocksize is ignored.
- e4defrag
- I/O engine that does regular EXT4_IOC_MOVE_EXT ioctls to simulate
defragment activity in request to DDIR_WRITE event.
- rados
- I/O engine supporting direct access to Ceph Reliable Autonomic Distributed
Object Store (RADOS) via librados. This ioengine defines engine specific
options.
- rbd
- I/O engine supporting direct access to Ceph Rados Block Devices (RBD) via
librbd without the need to use the kernel rbd driver. This ioengine
defines engine specific options.
- http
- I/O engine supporting GET/PUT requests over HTTP(S) with libcurl to a
WebDAV or S3 endpoint. This ioengine defines engine specific options.
This engine only supports direct IO of iodepth=1; you need to
scale this via numjobs. blocksize defines the size of the objects to be
created.
TRIM is translated to object deletion.
- gfapi
- Using GlusterFS libgfapi sync interface to direct access to GlusterFS
volumes without having to go through FUSE. This ioengine defines engine
specific options.
- gfapi_async
- Using GlusterFS libgfapi async interface to direct access to GlusterFS
volumes without having to go through FUSE. This ioengine defines engine
specific options.
- libhdfs
- Read and write through Hadoop (HDFS). The filename option is used
to specify host,port of the hdfs name-node to connect. This engine
interprets offsets a little differently. In HDFS, files once created
cannot be modified so random writes are not possible. To imitate this the
libhdfs engine expects a bunch of small files to be created over HDFS and
will randomly pick a file from them based on the offset generated by fio
backend (see the example job file to create such files, use `rw=write'
option). Please note, it may be necessary to set environment variables to
work with HDFS/libhdfs properly. Each job uses its own connection to
HDFS.
- mtd
- Read, write and erase an MTD character device (e.g., `/dev/mtd0').
Discards are treated as erases. Depending on the underlying device type,
the I/O may have to go in a certain pattern, e.g., on NAND, writing
sequentially to erase blocks and discarding before overwriting. The
trimwrite mode works well for this constraint.
- pmemblk
- Read and write using filesystem DAX to a file on a filesystem mounted with
DAX on a persistent memory device through the PMDK libpmemblk
library.
- dev-dax
- Read and write using device DAX to a persistent memory device (e.g.,
/dev/dax0.0) through the PMDK libpmem library.
- external
- Prefix to specify loading an external I/O engine object file. Append the
engine filename, e.g. `ioengine=external:/tmp/foo.o' to load ioengine
`foo.o' in `/tmp'. The path can be either absolute or relative. See
`engines/skeleton_external.c' in the fio source for details of writing an
external I/O engine.
- filecreate
- Simply create the files and do no I/O to them. You still need to set
filesize so that all the accounting still occurs, but no actual I/O
will be done other than creating the file.
- libpmem
- Read and write using mmap I/O to a file on a filesystem mounted with DAX
on a persistent memory device through the PMDK libpmem library.
- ime_psync
- Synchronous read and write using DDN's Infinite Memory Engine (IME). This
engine is very basic and issues calls to IME whenever an IO is
queued.
- ime_psyncv
- Synchronous read and write using DDN's Infinite Memory Engine (IME). This
engine uses iovecs and will try to stack as much IOs as possible (if the
IOs are "contiguous" and the IO depth is not exceeded) before
issuing a call to IME.
- ime_aio
- Asynchronous read and write using DDN's Infinite Memory Engine (IME). This
engine will try to stack as much IOs as possible by creating requests for
IME. FIO will then decide when to commit these requests.
In addition, there are some parameters which are only valid when a
specific ioengine is in use. These are used identically to normal
parameters, with the caveat that when used on the command line, they must
come after the ioengine that defines them is selected.
- (libaio)userspace_reap
- Normally, with the libaio engine in use, fio will use the
io_getevents(3) system call to reap newly returned events. With
this flag turned on, the AIO ring will be read directly from user-space to
reap events. The reaping mode is only enabled when polling for a minimum
of 0 events (e.g. when `iodepth_batch_complete=0').
- (pvsync2)hipri
- Set RWF_HIPRI on I/O, indicating to the kernel that it's of higher
priority than normal.
- (pvsync2)hipri_percentage
- When hipri is set this determines the probability of a pvsync2 I/O being
high priority. The default is 100%.
- (cpuio)cpuload=int
- Attempt to use the specified percentage of CPU cycles. This is a mandatory
option when using cpuio I/O engine.
- (cpuio)cpuchunks=int
- Split the load into cycles of the given time. In microseconds.
- (cpuio)exit_on_io_done=bool
- Detect when I/O threads are done, then exit.
- (libhdfs)namenode=str
- The hostname or IP address of a HDFS cluster namenode to contact.
- (libhdfs)port
- The listening port of the HFDS cluster namenode.
- (netsplice,net)port
- The TCP or UDP port to bind to or connect to. If this is used with
numjobs to spawn multiple instances of the same job type, then this
will be the starting port number since fio will use a range of ports.
- (rdma)port
- The port to use for RDMA-CM communication. This should be the same value
on the client and the server side.
- (netsplice,net,rdma)hostname=str
- The hostname or IP address to use for TCP, UDP or RDMA-CM based I/O. If
the job is a TCP listener or UDP reader, the hostname is not used and must
be omitted unless it is a valid UDP multicast address.
- (netsplice,net)interface=str
- The IP address of the network interface used to send or receive UDP
multicast.
- (netsplice,net)ttl=int
- Time-to-live value for outgoing UDP multicast packets. Default: 1.
- (netsplice,net)nodelay=bool
- Set TCP_NODELAY on TCP connections.
- (netsplice,net)protocol=str, proto=str
- The network protocol to use. Accepted values are:
- tcp
- Transmission control protocol.
- tcpv6
- Transmission control protocol V6.
- udp
- User datagram protocol.
- udpv6
- User datagram protocol V6.
- unix
- UNIX domain socket.
When the protocol is TCP or UDP, the port must also be given, as
well as the hostname if the job is a TCP listener or UDP reader. For unix
sockets, the normal filename option should be used and the port is
invalid.
- (netsplice,net)listen
- For TCP network connections, tell fio to listen for incoming connections
rather than initiating an outgoing connection. The hostname must be
omitted if this option is used.
- (netsplice,net)pingpong
- Normally a network writer will just continue writing data, and a network
reader will just consume packages. If `pingpong=1' is set, a writer will
send its normal payload to the reader, then wait for the reader to send
the same payload back. This allows fio to measure network latencies. The
submission and completion latencies then measure local time spent sending
or receiving, and the completion latency measures how long it took for the
other end to receive and send back. For UDP multicast traffic `pingpong=1'
should only be set for a single reader when multiple readers are listening
to the same address.
- (netsplice,net)window_size=int
- Set the desired socket buffer size for the connection.
- (netsplice,net)mss=int
- Set the TCP maximum segment size (TCP_MAXSEG).
- (e4defrag)donorname=str
- File will be used as a block donor (swap extents between files).
- (e4defrag)inplace=int
- Configure donor file blocks allocation strategy:
- 0
- Default. Preallocate donor's file on init.
- 1
- Allocate space immediately inside defragment event, and free right after
event.
- (rbd,rados)clustername=str
- Specifies the name of the Ceph cluster.
- (rbd)rbdname=str
- Specifies the name of the RBD.
- (rbd,rados)pool=str
- Specifies the name of the Ceph pool containing RBD or RADOS data.
- (rbd,rados)clientname=str
- Specifies the username (without the 'client.' prefix) used to access the
Ceph cluster. If the clustername is specified, the
clientname shall be the full *type.id* string. If no type. prefix
is given, fio will add 'client.' by default.
- (rbd,rados)busy_poll=bool
- Poll store instead of waiting for completion. Usually this provides better
throughput at cost of higher(up to 100%) CPU utilization.
- (http)http_host=str
- Hostname to connect to. For S3, this could be the bucket name. Default is
localhost
- (http)http_user=str
- Username for HTTP authentication.
- (http)http_pass=str
- Password for HTTP authentication.
- (http)https=str
- Whether to use HTTPS instead of plain HTTP. on enables HTTPS; insecure
will enable HTTPS, but disable SSL peer verification (use with caution!).
Default is off.
- (http)http_mode=str
- Which HTTP access mode to use: webdav, swift, or s3. Default is
webdav.
- (http)http_s3_region=str
- The S3 region/zone to include in the request. Default is
us-east-1.
- (http)http_s3_key=str
- The S3 secret key.
- (http)http_s3_keyid=str
- The S3 key/access id.
- (http)http_swift_auth_token=str
- The Swift auth token. See the example configuration file on how to
retrieve this.
- (http)http_verbose=int
- Enable verbose requests from libcurl. Useful for debugging. 1 turns on
verbose logging from libcurl, 2 additionally enables HTTP IO tracing.
Default is 0
- (mtd)skip_bad=bool
- Skip operations against known bad blocks.
- (libhdfs)hdfsdirectory
- libhdfs will create chunk in this HDFS directory.
- (libhdfs)chunk_size
- The size of the chunk to use for each file.
- (rdma)verb=str
- The RDMA verb to use on this side of the RDMA ioengine connection. Valid
values are write, read, send and recv. These correspond to the equivalent
RDMA verbs (e.g. write = rdma_write etc.). Note that this only needs to be
specified on the client side of the connection. See the examples
folder.
- (rdma)bindname=str
- The name to use to bind the local RDMA-CM connection to a local RDMA
device. This could be a hostname or an IPv4 or IPv6 address. On the server
side this will be passed into the rdma_bind_addr() function and on the
client site it will be used in the rdma_resolve_add() function. This can
be useful when multiple paths exist between the client and the server or
in certain loopback configurations.
- (sg)readfua=bool
- With readfua option set to 1, read operations include the force unit
access (fua) flag. Default: 0.
- (sg)writefua=bool
- With writefua option set to 1, write operations include the force unit
access (fua) flag. Default: 0.
- (sg)sg_write_mode=str
- Specify the type of write commands to issue. This option can take three
values:
- write (default)
- Write opcodes are issued as usual
- verify
- Issue WRITE AND VERIFY commands. The BYTCHK bit is set to 0. This directs
the device to carry out a medium verification with no data comparison. The
writefua option is ignored with this selection.
- same
- Issue WRITE SAME commands. This transfers a single block to the device and
writes this same block of data to a contiguous sequence of LBAs beginning
at the specified offset. fio's block size parameter specifies the amount
of data written with each command. However, the amount of data actually
transferred to the device is equal to the device's block (sector) size.
For a device with 512 byte sectors, blocksize=8k will write 16 sectors
with each command. fio will still generate 8k of data for each command
butonly the first 512 bytes will be used and transferred to the device.
The writefua option is ignored with this selection.
- iodepth=int
- Number of I/O units to keep in flight against the file. Note that
increasing iodepth beyond 1 will not affect synchronous ioengines
(except for small degrees when verify_async is in use). Even async
engines may impose OS restrictions causing the desired depth not to be
achieved. This may happen on Linux when using libaio and not setting
`direct=1', since buffered I/O is not async on that OS. Keep an eye on the
I/O depth distribution in the fio output to verify that the achieved depth
is as expected. Default: 1.
- iodepth_batch_submit=int,
iodepth_batch=int
- This defines how many pieces of I/O to submit at once. It defaults to 1
which means that we submit each I/O as soon as it is available, but can be
raised to submit bigger batches of I/O at the time. If it is set to 0 the
iodepth value will be used.
- iodepth_batch_complete_min=int,
iodepth_batch_complete=int
- This defines how many pieces of I/O to retrieve at once. It defaults to 1
which means that we'll ask for a minimum of 1 I/O in the retrieval process
from the kernel. The I/O retrieval will go on until we hit the limit set
by iodepth_low. If this variable is set to 0, then fio will always
check for completed events before queuing more I/O. This helps reduce I/O
latency, at the cost of more retrieval system calls.
- iodepth_batch_complete_max=int
- This defines maximum pieces of I/O to retrieve at once. This variable
should be used along with iodepth_batch_complete_min=int
variable, specifying the range of min and max amount of I/O which should
be retrieved. By default it is equal to iodepth_batch_complete_min
value. Example #1:
iodepth_batch_complete_min=1
iodepth_batch_complete_max=<iodepth>
which means that we will retrieve at least 1 I/O and up to the
whole submitted queue depth. If none of I/O has been completed yet, we will
wait. Example #2:
iodepth_batch_complete_min=0
iodepth_batch_complete_max=<iodepth>
which means that we can retrieve up to the whole submitted queue
depth, but if none of I/O has been completed yet, we will NOT wait and
immediately exit the system call. In this example we simply do polling.
- iodepth_low=int
- The low water mark indicating when to start filling the queue again.
Defaults to the same as iodepth, meaning that fio will attempt to
keep the queue full at all times. If iodepth is set to e.g. 16 and
iodepth_low is set to 4, then after fio has filled the queue of 16
requests, it will let the depth drain down to 4 before starting to fill it
again.
- serialize_overlap=bool
- Serialize in-flight I/Os that might otherwise cause or suffer from data
races. When two or more I/Os are submitted simultaneously, there is no
guarantee that the I/Os will be processed or completed in the submitted
order. Further, if two or more of those I/Os are writes, any overlapping
region between them can become indeterminate/undefined on certain storage.
These issues can cause verification to fail erratically when at least one
of the racing I/Os is changing data and the overlapping region has a
non-zero size. Setting serialize_overlap tells fio to avoid
provoking this behavior by explicitly serializing in-flight I/Os that have
a non-zero overlap. Note that setting this option can reduce both
performance and the iodepth achieved.
This option only applies to I/Os issued for a single job except
when it is enabled along with io_submit_mode=offload. In offload
mode, fio will check for overlap among all I/Os submitted by offload jobs
with serialize_overlap enabled.
Default: false.
- io_submit_mode=str
- This option controls how fio submits the I/O to the I/O engine. The
default is `inline', which means that the fio job threads submit and reap
I/O directly. If set to `offload', the job threads will offload I/O
submission to a dedicated pool of I/O threads. This requires some
coordination and thus has a bit of extra overhead, especially for lower
queue depth I/O where it can increase latencies. The benefit is that fio
can manage submission rates independently of the device completion rates.
This avoids skewed latency reporting if I/O gets backed up on the device
side (the coordinated omission problem).
- thinktime=time
- Stall the job for the specified period of time after an I/O has completed
before issuing the next. May be used to simulate processing being done by
an application. When the unit is omitted, the value is interpreted in
microseconds. See thinktime_blocks and thinktime_spin.
- thinktime_spin=time
- Only valid if thinktime is set - pretend to spend CPU time doing
something with the data received, before falling back to sleeping for the
rest of the period specified by thinktime. When the unit is
omitted, the value is interpreted in microseconds.
- thinktime_blocks=int
- Only valid if thinktime is set - control how many blocks to issue,
before waiting thinktime usecs. If not set, defaults to 1 which
will make fio wait thinktime usecs after every block. This
effectively makes any queue depth setting redundant, since no more than 1
I/O will be queued before we have to complete it and do our
thinktime. In other words, this setting effectively caps the queue
depth if the latter is larger.
- rate=int[,int][,int]
- Cap the bandwidth used by this job. The number is in bytes/sec, the normal
suffix rules apply. Comma-separated values may be specified for reads,
writes, and trims as described in blocksize.
For example, using `rate=1m,500k' would limit reads to 1MiB/sec
and writes to 500KiB/sec. Capping only reads or writes can be done with
`rate=,500k' or `rate=500k,' where the former will only limit writes (to
500KiB/sec) and the latter will only limit reads.
- rate_min=int[,int][,int]
- Tell fio to do whatever it can to maintain at least this bandwidth.
Failing to meet this requirement will cause the job to exit.
Comma-separated values may be specified for reads, writes, and trims as
described in blocksize.
- rate_iops=int[,int][,int]
- Cap the bandwidth to this number of IOPS. Basically the same as
rate, just specified independently of bandwidth. If the job is
given a block size range instead of a fixed value, the smallest block size
is used as the metric. Comma-separated values may be specified for reads,
writes, and trims as described in blocksize.
- rate_iops_min=int[,int][,int]
- If fio doesn't meet this rate of I/O, it will cause the job to exit.
Comma-separated values may be specified for reads, writes, and trims as
described in blocksize.
- rate_process=str
- This option controls how fio manages rated I/O submissions. The default is
`linear', which submits I/O in a linear fashion with fixed delays between
I/Os that gets adjusted based on I/O completion rates. If this is set to
`poisson', fio will submit I/O based on a more real world random request
flow, known as the Poisson process
(https://en.wikipedia.org/wiki/Poisson_point_process). The lambda
will be 10^6 / IOPS for the given workload.
- rate_ignore_thinktime=bool
- By default, fio will attempt to catch up to the specified rate setting, if
any kind of thinktime setting was used. If this option is set, then fio
will ignore the thinktime and continue doing IO at the specified rate,
instead of entering a catch-up mode after thinktime is done.
- latency_target=time
- If set, fio will attempt to find the max performance point that the given
workload will run at while maintaining a latency below this target. When
the unit is omitted, the value is interpreted in microseconds. See
latency_window and latency_percentile.
- latency_window=time
- Used with latency_target to specify the sample window that the job
is run at varying queue depths to test the performance. When the unit is
omitted, the value is interpreted in microseconds.
- latency_percentile=float
- The percentage of I/Os that must fall within the criteria specified by
latency_target and latency_window. If not set, this defaults
to 100.0, meaning that all I/Os must be equal or below to the value set by
latency_target.
- max_latency=time
- If set, fio will exit the job with an ETIMEDOUT error if it exceeds this
maximum latency. When the unit is omitted, the value is interpreted in
microseconds.
- rate_cycle=int
- Average bandwidth for rate and rate_min over this number of
milliseconds. Defaults to 1000.
- write_iolog=str
- Write the issued I/O patterns to the specified file. See
read_iolog. Specify a separate file for each job, otherwise the
iologs will be interspersed and the file may be corrupt.
- read_iolog=str
- Open an iolog with the specified filename and replay the I/O patterns it
contains. This can be used to store a workload and replay it sometime
later. The iolog given may also be a blktrace binary file, which allows
fio to replay a workload captured by blktrace. See blktrace(8) for
how to capture such logging data. For blktrace replay, the file needs to
be turned into a blkparse binary data file first (`blkparse <device>
-o /dev/null -d file_for_fio.bin'). You can specify a number of files by
separating the names with a ':' character. See the filename option
for information on how to escape ':' and '´ characters within the
file names. These files will be sequentially assigned to job clones
created by numjobs.
- read_iolog_chunked=bool
- Determines how iolog is read. If false (default) entire read_iolog
will be read at once. If selected true, input from iolog will be read
gradually. Useful when iolog is very large, or it is generated.
- merge_blktrace_file=str
- When specified, rather than replaying the logs passed to
read_iolog, the logs go through a merge phase which aggregates them
into a single blktrace. The resulting file is then passed on as the
read_iolog parameter. The intention here is to make the order of
events consistent. This limits the influence of the scheduler compared to
replaying multiple blktraces via concurrent jobs.
- merge_blktrace_scalars=float_list
- This is a percentage based option that is index paired with the list of
files passed to read_iolog. When merging is performed, scale the
time of each event by the corresponding amount. For example,
`--merge_blktrace_scalars="50:100"' runs the first trace in
halftime and the second trace in realtime. This knob is separately tunable
from replay_time_scale which scales the trace during runtime and
will not change the output of the merge unlike this option.
- merge_blktrace_iters=float_list
- This is a whole number option that is index paired with the list of files
passed to read_iolog. When merging is performed, run each trace for
the specified number of iterations. For example,
`--merge_blktrace_iters="2:1"' runs the first trace for two
iterations and the second trace for one iteration.
- replay_no_stall=bool
- When replaying I/O with read_iolog the default behavior is to
attempt to respect the timestamps within the log and replay them with the
appropriate delay between IOPS. By setting this variable fio will not
respect the timestamps and attempt to replay them as fast as possible
while still respecting ordering. The result is the same I/O pattern to a
given device, but different timings.
- replay_time_scale=int
- When replaying I/O with read_iolog, fio will honor the original
timing in the trace. With this option, it's possible to scale the time.
It's a percentage option, if set to 50 it means run at 50% the original IO
rate in the trace. If set to 200, run at twice the original IO rate.
Defaults to 100.
- replay_redirect=str
- While replaying I/O patterns using read_iolog the default behavior
is to replay the IOPS onto the major/minor device that each IOP was
recorded from. This is sometimes undesirable because on a different
machine those major/minor numbers can map to a different device. Changing
hardware on the same system can also result in a different major/minor
mapping. replay_redirect causes all I/Os to be replayed onto the
single specified device regardless of the device it was recorded from.
i.e. `replay_redirect=/dev/sdc' would cause all I/O in the blktrace or
iolog to be replayed onto `/dev/sdc'. This means multiple devices will be
replayed onto a single device, if the trace contains multiple devices. If
you want multiple devices to be replayed concurrently to multiple
redirected devices you must blkparse your trace into separate traces and
replay them with independent fio invocations. Unfortunately this also
breaks the strict time ordering between multiple device accesses.
- replay_align=int
- Force alignment of the byte offsets in a trace to this value. The value
must be a power of 2.
- replay_scale=int
- Scale bye offsets down by this factor when replaying traces. Should most
likely use replay_align as well.
- replay_skip=str
- Sometimes it's useful to skip certain IO types in a replay trace. This
could be, for instance, eliminating the writes in the trace. Or not
replaying the trims/discards, if you are redirecting to a device that
doesn't support them. This option takes a comma separated list of read,
write, trim, sync.
- thread
- Fio defaults to creating jobs by using fork, however if this option is
given, fio will create jobs by using POSIX Threads' function
pthread_create(3) to create threads instead.
- wait_for=str
- If set, the current job won't be started until all workers of the
specified waitee job are done. wait_for operates on the job name
basis, so there are a few limitations. First, the waitee must be defined
prior to the waiter job (meaning no forward references). Second, if a job
is being referenced as a waitee, it must have a unique name (no duplicate
waitees).
- nice=int
- Run the job with the given nice value. See man nice(2). On Windows,
values less than -15 set the process class to "High"; -1 through
-15 set "Above Normal"; 1 through 15 "Below Normal";
and above 15 "Idle" priority class.
- prio=int
- Set the I/O priority value of this job. Linux limits us to a positive
value between 0 and 7, with 0 being the highest. See man ionice(1).
Refer to an appropriate manpage for other operating systems since meaning
of priority may differ.
- prioclass=int
- Set the I/O priority class. See man ionice(1).
- cpus_allowed=str
- Controls the same options as cpumask, but accepts a textual
specification of the permitted CPUs instead and CPUs are indexed from 0.
So to use CPUs 0 and 5 you would specify `cpus_allowed=0,5'. This option
also allows a range of CPUs to be specified -- say you wanted a binding to
CPUs 0, 5, and 8 to 15, you would set `cpus_allowed=0,5,8-15'.
On Windows, when `cpus_allowed' is unset only CPUs from fio's
current processor group will be used and affinity settings are inherited
from the system. An fio build configured to target Windows 7 makes options
that set CPUs processor group aware and values will set both the processor
group and a CPU from within that group. For example, on a system where
processor group 0 has 40 CPUs and processor group 1 has 32 CPUs,
`cpus_allowed' values between 0 and 39 will bind CPUs from processor group 0
and `cpus_allowed' values between 40 and 71 will bind CPUs from processor
group 1. When using `cpus_allowed_policy=shared' all CPUs specified by a
single `cpus_allowed' option must be from the same processor group. For
Windows fio builds not built for Windows 7, CPUs will only be selected from
(and be relative to) whatever processor group fio happens to be running in
and CPUs from other processor groups cannot be used.
- cpus_allowed_policy=str
- Set the policy of how fio distributes the CPUs specified by
cpus_allowed or cpumask. Two policies are supported:
- shared
- All jobs will share the CPU set specified.
- split
- Each job will get a unique CPU from the CPU set.
shared is the default behavior, if the option isn't
specified. If split is specified, then fio will will assign one cpu
per job. If not enough CPUs are given for the jobs listed, then fio will
roundrobin the CPUs in the set.
- cpumask=int
- Set the CPU affinity of this job. The parameter given is a bit mask of
allowed CPUs the job may run on. So if you want the allowed CPUs to be 1
and 5, you would pass the decimal value of (1 << 1 | 1 << 5),
or 34. See man sched_setaffinity(2). This may not work on all
supported operating systems or kernel versions. This option doesn't work
well for a higher CPU count than what you can store in an integer mask, so
it can only control cpus 1-32. For boxes with larger CPU counts, use
cpus_allowed.
- numa_cpu_nodes=str
- Set this job running on specified NUMA nodes' CPUs. The arguments allow
comma delimited list of cpu numbers, A-B ranges, or `all'. Note, to enable
NUMA options support, fio must be built on a system with libnuma-dev(el)
installed.
- numa_mem_policy=str
- Set this job's memory policy and corresponding NUMA nodes. Format of the
arguments:
`mode' is one of the following memory policies: `default',
`prefer', `bind', `interleave' or `local'. For `default' and `local' memory
policies, no node needs to be specified. For `prefer', only one node is
allowed. For `bind' and `interleave' the `nodelist' may be as follows: a
comma delimited list of numbers, A-B ranges, or `all'.
- cgroup=str
- Add job to this control group. If it doesn't exist, it will be created.
The system must have a mounted cgroup blkio mount point for this to work.
If your system doesn't have it mounted, you can do so with:
# mount -t cgroup -o blkio none /cgroup
- cgroup_weight=int
- Set the weight of the cgroup to this value. See the documentation that
comes with the kernel, allowed values are in the range of 100..1000.
- cgroup_nodelete=bool
- Normally fio will delete the cgroups it has created after the job
completion. To override this behavior and to leave cgroups around after
the job completion, set `cgroup_nodelete=1'. This can be useful if one
wants to inspect various cgroup files after job completion. Default:
false.
- flow_id=int
- The ID of the flow. If not specified, it defaults to being a global flow.
See flow.
- flow=int
- Weight in token-based flow control. If this value is used, then there is a
'flow counter' which is used to regulate the proportion of activity
between two or more jobs. Fio attempts to keep this flow counter near
zero. The flow parameter stands for how much should be added or
subtracted to the flow counter on each iteration of the main I/O loop.
That is, if one job has `flow=8' and another job has `flow=-1', then there
will be a roughly 1:8 ratio in how much one runs vs the other.
- flow_watermark=int
- The maximum value that the absolute value of the flow counter is allowed
to reach before the job must wait for a lower value of the counter.
- flow_sleep=int
- The period of time, in microseconds, to wait after the flow watermark has
been exceeded before retrying operations.
- stonewall,
wait_for_previous
- Wait for preceding jobs in the job file to exit, before starting this one.
Can be used to insert serialization points in the job file. A stone wall
also implies starting a new reporting group, see
group_reporting.
- exitall
- By default, fio will continue running all other jobs when one job finishes
but sometimes this is not the desired action. Setting exitall will
instead make fio terminate all other jobs when one job finishes.
- exec_prerun=str
- Before running this job, issue the command specified through
system(3). Output is redirected in a file called
`jobname.prerun.txt'.
- exec_postrun=str
- After the job completes, issue the command specified though
system(3). Output is redirected in a file called
`jobname.postrun.txt'.
- uid=int
- Instead of running as the invoking user, set the user ID to this value
before the thread/process does any work.
- gid=int
- Set group ID, see uid.
- verify_only
- Do not perform specified workload, only verify data still matches previous
invocation of this workload. This option allows one to check data multiple
times at a later date without overwriting it. This option makes sense only
for workloads that write data, and does not support workloads with the
time_based option set.
- do_verify=bool
- Run the verify phase after a write phase. Only valid if verify is
set. Default: true.
- verify=str
- If writing to a file, fio can verify the file contents after each
iteration of the job. Each verification method also implies verification
of special header, which is written to the beginning of each block. This
header also includes meta information, like offset of the block, block
number, timestamp when block was written, etc. verify can be
combined with verify_pattern option. The allowed values are:
- md5
- Use an md5 sum of the data area and store it in the header of each
block.
- crc64
- Use an experimental crc64 sum of the data area and store it in the header
of each block.
- crc32c
- Use a crc32c sum of the data area and store it in the header of each
block. This will automatically use hardware acceleration (e.g. SSE4.2 on
an x86 or CRC crypto extensions on ARM64) but will fall back to software
crc32c if none is found. Generally the fastest checksum fio supports when
hardware accelerated.
- crc32c-intel
- Synonym for crc32c.
- crc32
- Use a crc32 sum of the data area and store it in the header of each
block.
- crc16
- Use a crc16 sum of the data area and store it in the header of each
block.
- crc7
- Use a crc7 sum of the data area and store it in the header of each
block.
- xxhash
- Use xxhash as the checksum function. Generally the fastest software
checksum that fio supports.
- sha512
- Use sha512 as the checksum function.
- sha256
- Use sha256 as the checksum function.
- sha1
- Use optimized sha1 as the checksum function.
- sha3-224
- Use optimized sha3-224 as the checksum function.
- sha3-256
- Use optimized sha3-256 as the checksum function.
- sha3-384
- Use optimized sha3-384 as the checksum function.
- sha3-512
- Use optimized sha3-512 as the checksum function.
- meta
- This option is deprecated, since now meta information is included in
generic verification header and meta verification happens by default. For
detailed information see the description of the verify setting.
This option is kept because of compatibility's sake with old
configurations. Do not use it.
- pattern
- Verify a strict pattern. Normally fio includes a header with some basic
information and checksumming, but if this option is set, only the specific
pattern set with verify_pattern is verified.
- null
- Only pretend to verify. Useful for testing internals with `ioengine=null',
not for much else.
This option can be used for repeated burn-in tests of a system to
make sure that the written data is also correctly read back. If the data
direction given is a read or random read, fio will assume that it should
verify a previously written file. If the data direction includes any form of
write, the verify will be of the newly written data.
To avoid false verification errors, do not use the norandommap
option when verifying data with async I/O engines and I/O depths > 1. Or
use the norandommap and the lfsr random generator together to avoid writing
to the same offset with muliple outstanding I/Os.
- verify_offset=int
- Swap the verification header with data somewhere else in the block before
writing. It is swapped back before verifying.
- verify_interval=int
- Write the verification header at a finer granularity than the
blocksize. It will be written for chunks the size of
verify_interval. blocksize should divide this evenly.
- verify_pattern=str
- If set, fio will fill the I/O buffers with this pattern. Fio defaults to
filling with totally random bytes, but sometimes it's interesting to fill
with a known pattern for I/O verification purposes. Depending on the width
of the pattern, fio will fill 1/2/3/4 bytes of the buffer at the time (it
can be either a decimal or a hex number). The verify_pattern if
larger than a 32-bit quantity has to be a hex number that starts with
either "0x" or "0X". Use with verify. Also,
verify_pattern supports %o format, which means that for each block
offset will be written and then verified back, e.g.:
Or use combination of everything:
verify_pattern=0xff%o"abcd"-12
- verify_fatal=bool
- Normally fio will keep checking the entire contents before quitting on a
block verification failure. If this option is set, fio will exit the job
on the first observed failure. Default: false.
- verify_dump=bool
- If set, dump the contents of both the original data block and the data
block we read off disk to files. This allows later analysis to inspect
just what kind of data corruption occurred. Off by default.
- verify_async=int
- Fio will normally verify I/O inline from the submitting thread. This
option takes an integer describing how many async offload threads to
create for I/O verification instead, causing fio to offload the duty of
verifying I/O contents to one or more separate threads. If using this
offload option, even sync I/O engines can benefit from using an
iodepth setting higher than 1, as it allows them to have I/O in
flight while verifies are running. Defaults to 0 async threads, i.e.
verification is not asynchronous.
- verify_async_cpus=str
- Tell fio to set the given CPU affinity on the async I/O verification
threads. See cpus_allowed for the format used.
- verify_backlog=int
- Fio will normally verify the written contents of a job that utilizes
verify once that job has completed. In other words, everything is written
then everything is read back and verified. You may want to verify
continually instead for a variety of reasons. Fio stores the meta data
associated with an I/O block in memory, so for large verify workloads,
quite a bit of memory would be used up holding this meta data. If this
option is enabled, fio will write only N blocks before verifying these
blocks.
- verify_backlog_batch=int
- Control how many blocks fio will verify if verify_backlog is set.
If not set, will default to the value of verify_backlog (meaning
the entire queue is read back and verified). If
verify_backlog_batch is less than verify_backlog then not
all blocks will be verified, if verify_backlog_batch is larger than
verify_backlog, some blocks will be verified more than once.
- verify_state_save=bool
- When a job exits during the write phase of a verify workload, save its
current state. This allows fio to replay up until that point, if the
verify state is loaded for the verify read phase. The format of the
filename is, roughly:
<type>-<jobname>-<jobindex>-verify.state.
<type> is "local" for a local run,
"sock" for a client/server socket connection, and "ip"
(192.168.0.1, for instance) for a networked client/server connection.
Defaults to true.
- verify_state_load=bool
- If a verify termination trigger was used, fio stores the current write
state of each thread. This can be used at verification time so that fio
knows how far it should verify. Without this information, fio will run a
full verification pass, according to the settings in the job file used.
Default false.
- trim_percentage=int
- Number of verify blocks to discard/trim.
- trim_verify_zero=bool
- Verify that trim/discarded blocks are returned as zeros.
- trim_backlog=int
- Verify that trim/discarded blocks are returned as zeros.
- trim_backlog_batch=int
- Trim this number of I/O blocks.
- experimental_verify=bool
- Enable experimental verification.
- steadystate=str:float,
ss=str:float
- Define the criterion and limit for assessing steady state performance. The
first parameter designates the criterion whereas the second parameter sets
the threshold. When the criterion falls below the threshold for the
specified duration, the job will stop. For example, `iops_slope:0.1%' will
direct fio to terminate the job when the least squares regression slope
falls below 0.1% of the mean IOPS. If group_reporting is enabled
this will apply to all jobs in the group. Below is the list of available
steady state assessment criteria. All assessments are carried out using
only data from the rolling collection window. Threshold limits can be
expressed as a fixed value or as a percentage of the mean in the
collection window.
When using this feature, most jobs should include the
time_based and runtime options or the loops option so
that fio does not stop running after it has covered the full size of the
specified file(s) or device(s).
- iops
- Collect IOPS data. Stop the job if all individual IOPS measurements are
within the specified limit of the mean IOPS (e.g., `iops:2' means that all
individual IOPS values must be within 2 of the mean, whereas `iops:0.2%'
means that all individual IOPS values must be within 0.2% of the mean IOPS
to terminate the job).
- iops_slope
- Collect IOPS data and calculate the least squares regression slope. Stop
the job if the slope falls below the specified limit.
- bw
- Collect bandwidth data. Stop the job if all individual bandwidth
measurements are within the specified limit of the mean bandwidth.
- bw_slope
- Collect bandwidth data and calculate the least squares regression slope.
Stop the job if the slope falls below the specified limit.
- steadystate_duration=time,
ss_dur=time
- A rolling window of this duration will be used to judge whether steady
state has been reached. Data will be collected once per second. The
default is 0 which disables steady state detection. When the unit is
omitted, the value is interpreted in seconds.
- steadystate_ramp_time=time,
ss_ramp=time
- Allow the job to run for the specified duration before beginning data
collection for checking the steady state job termination criterion. The
default is 0. When the unit is omitted, the value is interpreted in
seconds.
- per_job_logs=bool
- If set, this generates bw/clat/iops log with per file private filenames.
If not set, jobs with identical names will share the log filename.
Default: true.
- group_reporting
- It may sometimes be interesting to display statistics for groups of jobs
as a whole instead of for each individual job. This is especially true if
numjobs is used; looking at individual thread/process output
quickly becomes unwieldy. To see the final report per-group instead of
per-job, use group_reporting. Jobs in a file will be part of the
same reporting group, unless if separated by a stonewall, or by
using new_group.
- new_group
- Start a new reporting group. See: group_reporting. If not given,
all jobs in a file will be part of the same reporting group, unless
separated by a stonewall.
- stats=bool
- By default, fio collects and shows final output results for all jobs that
run. If this option is set to 0, then fio will ignore it in the final stat
output.
- write_bw_log=str
- If given, write a bandwidth log for this job. Can be used to store data of
the bandwidth of the jobs in their lifetime.
If no str argument is given, the default filename of
`jobname_type.x.log' is used. Even when the argument is given, fio will
still append the type of log. So if one specifies:
The actual log name will be `foo_bw.x.log' where `x' is the index
of the job (1..N, where N is the number of jobs). If per_job_logs is
false, then the filename will not include the `.x` job index.
The included fio_generate_plots script uses gnuplot to turn
these text files into nice graphs. See the LOG FILE FORMATS section
for how data is structured within the file.
- write_lat_log=str
- Same as write_bw_log, except this option creates I/O submission
(e.g., `name_slat.x.log'), completion (e.g., `name_clat.x.log'), and total
(e.g., `name_lat.x.log') latency files instead. See write_bw_log
for details about the filename format and the LOG FILE FORMATS
section for how data is structured within the files.
- write_hist_log=str
- Same as write_bw_log but writes an I/O completion latency histogram
file (e.g., `name_hist.x.log') instead. Note that this file will be empty
unless log_hist_msec has also been set. See write_bw_log for
details about the filename format and the LOG FILE FORMATS section
for how data is structured within the file.
- write_iops_log=str
- Same as write_bw_log, but writes an IOPS file (e.g.
`name_iops.x.log`) instead. Because fio defaults to individual I/O
logging, the value entry in the IOPS log will be 1 unless windowed logging
(see log_avg_msec) has been enabled. See write_bw_log for
details about the filename format and LOG FILE FORMATS for
how data is structured within the file.
- log_avg_msec=int
- By default, fio will log an entry in the iops, latency, or bw log for
every I/O that completes. When writing to the disk log, that can quickly
grow to a very large size. Setting this option makes fio average the each
log entry over the specified period of time, reducing the resolution of
the log. See log_max_value as well. Defaults to 0, logging all
entries. Also see LOG FILE FORMATS section.
- log_hist_msec=int
- Same as log_avg_msec, but logs entries for completion latency
histograms. Computing latency percentiles from averages of intervals using
log_avg_msec is inaccurate. Setting this option makes fio log
histogram entries over the specified period of time, reducing log sizes
for high IOPS devices while retaining percentile accuracy. See
log_hist_coarseness and write_hist_log as well. Defaults to
0, meaning histogram logging is disabled.
- log_hist_coarseness=int
- Integer ranging from 0 to 6, defining the coarseness of the resolution of
the histogram logs enabled with log_hist_msec. For each increment
in coarseness, fio outputs half as many bins. Defaults to 0, for which
histogram logs contain 1216 latency bins. See LOG FILE FORMATS
section.
- log_max_value=bool
- If log_avg_msec is set, fio logs the average over that window. If
you instead want to log the maximum value, set this option to 1. Defaults
to 0, meaning that averaged values are logged.
- log_offset=bool
- If this is set, the iolog options will include the byte offset for the I/O
entry as well as the other data values. Defaults to 0 meaning that offsets
are not present in logs. Also see LOG FILE FORMATS section.
- log_compression=int
- If this is set, fio will compress the I/O logs as it goes, to keep the
memory footprint lower. When a log reaches the specified size, that chunk
is removed and compressed in the background. Given that I/O logs are
fairly highly compressible, this yields a nice memory savings for longer
runs. The downside is that the compression will consume some background
CPU cycles, so it may impact the run. This, however, is also true if the
logging ends up consuming most of the system memory. So pick your poison.
The I/O logs are saved normally at the end of a run, by decompressing the
chunks and storing them in the specified log file. This feature depends on
the availability of zlib.
- log_compression_cpus=str
- Define the set of CPUs that are allowed to handle online log compression
for the I/O jobs. This can provide better isolation between performance
sensitive jobs, and background compression work. See cpus_allowed
for the format used.
- log_store_compressed=bool
- If set, fio will store the log files in a compressed format. They can be
decompressed with fio, using the --inflate-log command line
parameter. The files will be stored with a `.fz' suffix.
- log_unix_epoch=bool
- If set, fio will log Unix timestamps to the log files produced by enabling
write_type_log for each log type, instead of the default zero-based
timestamps.
- block_error_percentiles=bool
- If set, record errors in trim block-sized units from writes and trims and
output a histogram of how many trims it took to get to errors, and what
kind of error was encountered.
- bwavgtime=int
- Average the calculated bandwidth over the given time. Value is specified
in milliseconds. If the job also does bandwidth logging through
write_bw_log, then the minimum of this option and
log_avg_msec will be used. Default: 500ms.
- iopsavgtime=int
- Average the calculated IOPS over the given time. Value is specified in
milliseconds. If the job also does IOPS logging through
write_iops_log, then the minimum of this option and
log_avg_msec will be used. Default: 500ms.
- disk_util=bool
- Generate disk utilization statistics, if the platform supports it.
Default: true.
- disable_lat=bool
- Disable measurements of total latency numbers. Useful only for cutting
back the number of calls to gettimeofday(2), as that does impact
performance at really high IOPS rates. Note that to really get rid of a
large amount of these calls, this option must be used with
disable_slat and disable_bw_measurement as well.
- disable_clat=bool
- Disable measurements of completion latency numbers. See
disable_lat.
- disable_slat=bool
- Disable measurements of submission latency numbers. See
disable_lat.
- disable_bw_measurement=bool,
disable_bw=bool
- Disable measurements of throughput/bandwidth numbers. See
disable_lat.
- clat_percentiles=bool
- Enable the reporting of percentiles of completion latencies. This option
is mutually exclusive with lat_percentiles.
- lat_percentiles=bool
- Enable the reporting of percentiles of I/O latencies. This is similar to
clat_percentiles, except that this includes the submission latency.
This option is mutually exclusive with clat_percentiles.
- percentile_list=float_list
- Overwrite the default list of percentiles for completion latencies and the
block error histogram. Each number is a floating number in the range
(0,100], and the maximum length of the list is 20. Use ':' to separate the
numbers, and list the numbers in ascending order. For example,
`--percentile_list=99.5:99.9' will cause fio to report the values of
completion latency below which 99.5% and 99.9% of the observed latencies
fell, respectively.
- significant_figures=int
- If using --output-format of `normal', set the significant figures
to this value. Higher values will yield more precise IOPS and throughput
units, while lower values will round. Requires a minimum value of 1 and a
maximum value of 10. Defaults to 4.
- exitall_on_error
- When one job finishes in error, terminate the rest. The default is to wait
for each job to finish.
- continue_on_error=str
- Normally fio will exit the job on the first observed failure. If this
option is set, fio will continue the job when there is a 'non-fatal error'
(EIO or EILSEQ) until the runtime is exceeded or the I/O size specified is
completed. If this option is used, there are two more stats that are
appended, the total error count and the first error. The error field given
in the stats is the first error that was hit during the run. The allowed
values are:
- none
- Exit on any I/O or verify errors.
- read
- Continue on read errors, exit on all others.
- write
- Continue on write errors, exit on all others.
- io
- Continue on any I/O error, exit on all others.
- verify
- Continue on verify errors, exit on all others.
- all
- Continue on all errors.
- 0
- Backward-compatible alias for 'none'.
- 1
- Backward-compatible alias for 'all'.
- ignore_error=str
- Sometimes you want to ignore some errors during test in that case you can
specify error list for each error type, instead of only being able to
ignore the default 'non-fatal error' using continue_on_error.
`ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST' errors for
given error type is separated with ':'. Error may be symbol ('ENOSPC',
'ENOMEM') or integer. Example:
ignore_error=EAGAIN,ENOSPC:122
This option will ignore EAGAIN from READ, and ENOSPC and
122(EDQUOT) from WRITE. This option works by overriding
continue_on_error with the list of errors for each error type if
any.
- error_dump=bool
- If set dump every error even if it is non fatal, true by default. If
disabled only fatal error will be dumped.
Fio includes predefined profiles that mimic the I/O workloads
generated by other tools.
- profile=str
- The predefined workload to run. Current profiles are:
- tiobench
- Threaded I/O bench (tiotest/tiobench) like workload.
- act
- Aerospike Certification Tool (ACT) like workload.
To view a profile's additional options use --cmdhelp after
specifying the profile. For example:
- $ fio --profile=act --cmdhelp
- device-names=str
- Devices to use.
- load=int
- ACT load multiplier. Default: 1.
- test-duration=time
- How long the entire test takes to run. When the unit is omitted, the value
is given in seconds. Default: 24h.
- threads-per-queue=int
- Number of read I/O threads per device. Default: 8.
- read-req-num-512-blocks=int
- Number of 512B blocks to read at the time. Default: 3.
- large-block-op-kbytes=int
- Size of large block ops in KiB (writes). Default: 131072.
- prep
- Set to run ACT prep phase.
Fio spits out a lot of output. While running, fio will display the
status of the jobs created. An example of that would be:
Jobs: 1 (f=1): [_(1),M(1)][24.8%][r=20.5MiB/s,w=23.5MiB/s][r=82,w=94 IOPS][eta 01m:31s]
The characters inside the first set of square brackets denote the
current status of each thread. The first character is the first job defined
in the job file, and so forth. The possible values (in typical life cycle
order) are:
- P
- Thread setup, but not started.
- C
- Thread created.
- I
- Thread initialized, waiting or generating necessary data.
- p
- Thread running pre-reading file(s).
- /
- Thread is in ramp period.
- R
- Running, doing sequential reads.
- r
- Running, doing random reads.
- W
- Running, doing sequential writes.
- w
- Running, doing random writes.
- M
- Running, doing mixed sequential reads/writes.
- m
- Running, doing mixed random reads/writes.
- D
- Running, doing sequential trims.
- d
- Running, doing random trims.
- F
- Running, currently waiting for fsync(2).
- V
- Running, doing verification of written data.
- f
- Thread finishing.
- E
- Thread exited, not reaped by main thread yet.
- -
- Thread reaped.
- X
- Thread reaped, exited with an error.
- K
- Thread reaped, exited due to signal.
Fio will condense the thread string as not to take up more space
on the command line than needed. For instance, if you have 10 readers and 10
writers running, the output would look like this:
Jobs: 20 (f=20): [R(10),W(10)][4.0%][r=20.5MiB/s,w=23.5MiB/s][r=82,w=94 IOPS][eta 57m:36s]
Note that the status string is displayed in order, so it's
possible to tell which of the jobs are currently doing what. In the example
above this means that jobs 1--10 are readers and 11--20 are writers.
The other values are fairly self explanatory -- number of threads
currently running and doing I/O, the number of currently open files (f=),
the estimated completion percentage, the rate of I/O since last check (read
speed listed first, then write speed and optionally trim speed) in terms of
bandwidth and IOPS, and time to completion for the current running group.
It's impossible to estimate runtime of the following groups (if any).
When fio is done (or interrupted by Ctrl-C), it will show the data
for each thread, group of threads, and disks in that order. For each overall
thread (or group) the output looks like:
Client1: (groupid=0, jobs=1): err= 0: pid=16109: Sat Jun 24 12:07:54 2017
write: IOPS=88, BW=623KiB/s (638kB/s)(30.4MiB/50032msec)
slat (nsec): min=500, max=145500, avg=8318.00, stdev=4781.50
clat (usec): min=170, max=78367, avg=4019.02, stdev=8293.31
lat (usec): min=174, max=78375, avg=4027.34, stdev=8291.79
clat percentiles (usec):
| 1.00th=[ 302], 5.00th=[ 326], 10.00th=[ 343], 20.00th=[ 363],
| 30.00th=[ 392], 40.00th=[ 404], 50.00th=[ 416], 60.00th=[ 445],
| 70.00th=[ 816], 80.00th=[ 6718], 90.00th=[12911], 95.00th=[21627],
| 99.00th=[43779], 99.50th=[51643], 99.90th=[68682], 99.95th=[72877],
| 99.99th=[78119]
bw ( KiB/s): min= 532, max= 686, per=0.10%, avg=622.87, stdev=24.82, samples= 100
iops : min= 76, max= 98, avg=88.98, stdev= 3.54, samples= 100
lat (usec) : 250=0.04%, 500=64.11%, 750=4.81%, 1000=2.79%
lat (msec) : 2=4.16%, 4=1.84%, 10=4.90%, 20=11.33%, 50=5.37%
lat (msec) : 100=0.65%
cpu : usr=0.27%, sys=0.18%, ctx=12072, majf=0, minf=21
IO depths : 1=85.0%, 2=13.1%, 4=1.8%, 8=0.1%, 16=0.0%, 32=0.0%, >=64=0.0%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
issued rwt: total=0,4450,0, short=0,0,0, dropped=0,0,0
latency : target=0, window=0, percentile=100.00%, depth=8
The job name (or first job's name when using
group_reporting) is printed, along with the group id, count of jobs
being aggregated, last error id seen (which is 0 when there are no errors),
pid/tid of that thread and the time the job/group completed. Below are the
I/O statistics for each data direction performed (showing writes in the
example above). In the order listed, they denote:
- read/write/trim
- The string before the colon shows the I/O direction the statistics are
for. IOPS is the average I/Os performed per second. BW is
the average bandwidth rate shown as: value in power of 2 format (value in
power of 10 format). The last two values show: (total I/O performed in
power of 2 format / runtime of that thread).
- slat
- Submission latency (min being the minimum, max being the
maximum, avg being the average, stdev being the standard
deviation). This is the time it took to submit the I/O. For sync I/O this
row is not displayed as the slat is really the completion latency (since
queue/complete is one operation there). This value can be in nanoseconds,
microseconds or milliseconds --- fio will choose the most appropriate base
and print that (in the example above nanoseconds was the best scale).
Note: in --minimal mode latencies are always expressed in
microseconds.
- clat
- Completion latency. Same names as slat, this denotes the time from
submission to completion of the I/O pieces. For sync I/O, clat will
usually be equal (or very close) to 0, as the time from submit to complete
is basically just CPU time (I/O has already been done, see slat
explanation).
- lat
- Total latency. Same names as slat and clat, this denotes the time from
when fio created the I/O unit to completion of the I/O operation.
- bw
- Bandwidth statistics based on samples. Same names as the xlat stats, but
also includes the number of samples taken (samples) and an
approximate percentage of total aggregate bandwidth this thread received
in its group (per). This last value is only really useful if the
threads in this group are on the same disk, since they are then competing
for disk access.
- iops
- IOPS statistics based on samples. Same names as bw.
- lat (nsec/usec/msec)
- The distribution of I/O completion latencies. This is the time from when
I/O leaves fio and when it gets completed. Unlike the separate
read/write/trim sections above, the data here and in the remaining
sections apply to all I/Os for the reporting group. 250=0.04% means that
0.04% of the I/Os completed in under 250us. 500=64.11% means that 64.11%
of the I/Os required 250 to 499us for completion.
- cpu
- CPU usage. User and system time, along with the number of context switches
this thread went through, usage of system and user time, and finally the
number of major and minor page faults. The CPU utilization numbers are
averages for the jobs in that reporting group, while the context and fault
counters are summed.
- IO depths
- The distribution of I/O depths over the job lifetime. The numbers are
divided into powers of 2 and each entry covers depths from that value up
to those that are lower than the next entry -- e.g., 16= covers depths
from 16 to 31. Note that the range covered by a depth distribution entry
can be different to the range covered by the equivalent
submit/complete distribution entry.
- IO submit
- How many pieces of I/O were submitting in a single submit call. Each entry
denotes that amount and below, until the previous entry -- e.g., 16=100%
means that we submitted anywhere between 9 to 16 I/Os per submit call.
Note that the range covered by a submit distribution entry can be
different to the range covered by the equivalent depth distribution
entry.
- IO complete
- Like the above submit number, but for completions instead.
- IO issued rwt
- The number of read/write/trim requests issued, and how many of them
were short or dropped.
- IO latency
- These values are for latency_target and related options. When these
options are engaged, this section describes the I/O depth required to meet
the specified latency target.
After each client has been listed, the group statistics are
printed. They will look like this:
Run status group 0 (all jobs):
READ: bw=20.9MiB/s (21.9MB/s), 10.4MiB/s-10.8MiB/s (10.9MB/s-11.3MB/s), io=64.0MiB (67.1MB), run=2973-3069msec
WRITE: bw=1231KiB/s (1261kB/s), 616KiB/s-621KiB/s (630kB/s-636kB/s), io=64.0MiB (67.1MB), run=52747-53223msec
For each data direction it prints:
- bw
- Aggregate bandwidth of threads in this group followed by the minimum and
maximum bandwidth of all the threads in this group. Values outside of
brackets are power-of-2 format and those within are the equivalent value
in a power-of-10 format.
- io
- Aggregate I/O performed of all threads in this group. The format is the
same as bw.
- run
- The smallest and longest runtimes of the threads in this group.
And finally, the disk statistics are printed. This is Linux
specific. They will look like this:
Disk stats (read/write):
sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
Each value is printed for both reads and writes, with reads first.
The numbers denote:
- ios
- Number of I/Os performed by all groups.
- merge
- Number of merges performed by the I/O scheduler.
- ticks
- Number of ticks we kept the disk busy.
- in_queue
- Total time spent in the disk queue.
- util
- The disk utilization. A value of 100% means we kept the disk busy
constantly, 50% would be a disk idling half of the time.
It is also possible to get fio to dump the current output while it
is running, without terminating the job. To do that, send fio the USR1
signal. You can also get regularly timed dumps by using the
--status-interval parameter, or by creating a file in `/tmp' named
`fio-dump-status'. If fio sees this file, it will unlink it and dump the
current output status.
For scripted usage where you typically want to generate tables or
graphs of the results, fio can output the results in a semicolon separated
format. The format is one long line of values, such as:
2;card0;0;0;7139336;121836;60004;1;10109;27.932460;116.933948;220;126861;3495.446807;1085.368601;226;126864;3523.635629;1089.012448;24063;99944;50.275485%;59818.274627;5540.657370;7155060;122104;60004;1;8338;29.086342;117.839068;388;128077;5032.488518;1234.785715;391;128085;5061.839412;1236.909129;23436;100928;50.287926%;59964.832030;5644.844189;14.595833%;19.394167%;123706;0;7313;0.1%;0.1%;0.1%;0.1%;0.1%;0.1%;100.0%;0.00%;0.00%;0.00%;0.00%;0.00%;0.00%;0.01%;0.02%;0.05%;0.16%;6.04%;40.40%;52.68%;0.64%;0.01%;0.00%;0.01%;0.00%;0.00%;0.00%;0.00%;0.00%
A description of this job goes here.
The job description (if provided) follows on a second line.
To enable terse output, use the --minimal or
`--output-format=terse' command line options. The first value is the version
of the terse output format. If the output has to be changed for some reason,
this number will be incremented by 1 to signify that change.
Split up, the format is as follows (comments in brackets denote
when a field was introduced or whether it's specific to some terse
version):
terse version, fio version [v3], jobname, groupid, error
Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
Submission latency: min, max, mean, stdev (usec)
Completion latency: min, max, mean, stdev (usec)
Completion latency percentiles: 20 fields (see below)
Total latency: min, max, mean, stdev (usec)
Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
IOPS [v5]: min, max, mean, stdev, number of samples
Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
Submission latency: min, max, mean, stdev (usec)
Completion latency: min, max, mean, stdev (usec)
Completion latency percentiles: 20 fields (see below)
Total latency: min, max, mean, stdev (usec)
Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
IOPS [v5]: min, max, mean, stdev, number of samples
TRIM status [all but version 3]:
Fields are similar to READ/WRITE status.
user, system, context switches, major faults, minor faults
<=1, 2, 4, 8, 16, 32, >=64
I/O latencies microseconds:
<=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000
I/O latencies milliseconds:
<=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000
disk name, read ios, write ios, read merges, write merges, read ticks, write ticks, time spent in queue, disk utilization percentage
Additional Info (dependent on continue_on_error, default
off):
total # errors, first error code
Additional Info (dependent on description being set):
Text description
Completion latency percentiles can be a grouping of up to 20 sets,
so for the terse output fio writes all of them. Each field will look like
this:
1.00%=6112
which is the Xth percentile, and the `usec' latency associated
with it.
For Disk utilization, all disks used by fio are shown. So
for each disk there will be a disk utilization section.
Below is a single line containing short names for each of the
fields in the minimal output v3, separated by semicolons:
terse_version_3;fio_version;jobname;groupid;error;read_kb;read_bandwidth;read_iops;read_runtime_ms;read_slat_min;read_slat_max;read_slat_mean;read_slat_dev;read_clat_min;read_clat_max;read_clat_mean;read_clat_dev;read_clat_pct01;read_clat_pct02;read_clat_pct03;read_clat_pct04;read_clat_pct05;read_clat_pct06;read_clat_pct07;read_clat_pct08;read_clat_pct09;read_clat_pct10;read_clat_pct11;read_clat_pct12;read_clat_pct13;read_clat_pct14;read_clat_pct15;read_clat_pct16;read_clat_pct17;read_clat_pct18;read_clat_pct19;read_clat_pct20;read_tlat_min;read_lat_max;read_lat_mean;read_lat_dev;read_bw_min;read_bw_max;read_bw_agg_pct;read_bw_mean;read_bw_dev;write_kb;write_bandwidth;write_iops;write_runtime_ms;write_slat_min;write_slat_max;write_slat_mean;write_slat_dev;write_clat_min;write_clat_max;write_clat_mean;write_clat_dev;write_clat_pct01;write_clat_pct02;write_clat_pct03;write_clat_pct04;write_clat_pct05;write_clat_pct06;write_clat_pct07;write_clat_pct08;write_clat_pct09;write_clat_pct10;write_clat_pct11;write_clat_pct12;write_clat_pct13;write_clat_pct14;write_clat_pct15;write_clat_pct16;write_clat_pct17;write_clat_pct18;write_clat_pct19;write_clat_pct20;write_tlat_min;write_lat_max;write_lat_mean;write_lat_dev;write_bw_min;write_bw_max;write_bw_agg_pct;write_bw_mean;write_bw_dev;cpu_user;cpu_sys;cpu_csw;cpu_mjf;cpu_minf;iodepth_1;iodepth_2;iodepth_4;iodepth_8;iodepth_16;iodepth_32;iodepth_64;lat_2us;lat_4us;lat_10us;lat_20us;lat_50us;lat_100us;lat_250us;lat_500us;lat_750us;lat_1000us;lat_2ms;lat_4ms;lat_10ms;lat_20ms;lat_50ms;lat_100ms;lat_250ms;lat_500ms;lat_750ms;lat_1000ms;lat_2000ms;lat_over_2000ms;disk_name;disk_read_iops;disk_write_iops;disk_read_merges;disk_write_merges;disk_read_ticks;write_ticks;disk_queue_time;disk_util
The json output format is intended to be both human
readable and convenient for automated parsing. For the most part its
sections mirror those of the normal output. The runtime value
is reported in msec and the bw value is reported in 1024 bytes per
second units.
The json+ output format is identical to the json
output format except that it adds a full dump of the completion latency
bins. Each bins object contains a set of (key, value) pairs where
keys are latency durations and values count how many I/Os had completion
latencies of the corresponding duration. For example, consider:
"bins" : { "87552" : 1, "89600" : 1,
"94720" : 1, "96768" : 1, "97792" : 1,
"99840" : 1, "100864" : 2, "103936" : 6,
"104960" : 534, "105984" : 5995, "107008" :
7529, ... }
This data indicates that one I/O required 87,552ns to complete,
two I/Os required 100,864ns to complete, and 7529 I/Os required 107,008ns to
complete.
Also included with fio is a Python script
fio_jsonplus_clat2csv that takes json+ output and generates
CSV-formatted latency data suitable for plotting.
The latency durations actually represent the midpoints of latency
intervals. For details refer to `stat.h' in the fio source.
There are two trace file format that you can encounter. The older
(v1) format is unsupported since version 1.20-rc3 (March 2008). It will
still be described below in case that you get an old trace and want to
understand it.
In any case the trace is a simple text file with a single action
per line.
- Trace file format
v1
- Each line represents a single I/O action in the following format:
where `rw=0/1' for read/write, and the `offset' and `length'
entries being in bytes.
This format is not supported in fio versions >= 1.20-rc3.
- Trace file format
v2
- The second version of the trace file format was added in fio version 1.17.
It allows to access more then one file per trace and has a bigger set of
possible file actions.
The first line of the trace file has to be:
Following this can be lines in two different formats, which are
described below.
The file management format:
filename action
The `filename' is given as an absolute path. The `action' can be
one of these:
- add
- Add the given `filename' to the trace.
- open
- Open the file with the given `filename'. The `filename' has to have been
added with the add action before.
- close
- Close the file with the given `filename'. The file has to have been
opened before.
The file I/O action format:
filename action offset length
The `filename' is given as an absolute path, and has to have been
added and opened before it can be used with this format. The
`offset' and `length' are given in bytes. The `action' can be one of
these:
- wait
- Wait for `offset' microseconds. Everything below 100 is discarded. The
time is relative to the previous `wait' statement.
- read
- Read `length' bytes beginning from `offset'.
- write
- Write `length' bytes beginning from `offset'.
- sync
- fsync(2) the file.
- datasync
- fdatasync(2) the file.
- trim
- Trim the given file from the given `offset' for `length' bytes.
Colocation is a common practice used to get the most out of a
machine. Knowing which workloads play nicely with each other and which ones
don't is a much harder task. While fio can replay workloads concurrently via
multiple jobs, it leaves some variability up to the scheduler making results
harder to reproduce. Merging is a way to make the order of events
consistent.
Merging is integrated into I/O replay and done when a
merge_blktrace_file is specified. The list of files passed to
read_iolog go through the merge process and output a single file
stored to the specified file. The output file is passed on as if it were the
only file passed to read_iolog. An example would look like:
$ fio --read_iolog="<file1>:<file2>"
--merge_blktrace_file="<output_file>"
Creating only the merged file can be done by passing the command
line argument merge-blktrace-only.
Scaling traces can be done to see the relative impact of any
particular trace being slowed down or sped up. merge_blktrace_scalars
takes in a colon separated list of percentage scalars. It is index paired
with the files passed to read_iolog.
With scaling, it may be desirable to match the running time of all
traces. This can be done with merge_blktrace_iters. It is index
paired with read_iolog just like merge_blktrace_scalars.
In an example, given two traces, A and B, each 60s long. If we
want to see the impact of trace A issuing IOs twice as fast and repeat trace
A over the runtime of trace B, the following can be done:
$ fio
--read_iolog="<trace_a>:"<trace_b>"
--merge_blktrace_file"<output_file>"
--merge_blktrace_scalars="50:100"
--merge_blktrace_iters="2:1"
This runs trace A at 2x the speed twice for approximately the same
runtime as a single run of trace B.
In some cases, we want to understand CPU overhead in a test. For
example, we test patches for the specific goodness of whether they reduce
CPU usage. Fio implements a balloon approach to create a thread per CPU that
runs at idle priority, meaning that it only runs when nobody else needs the
cpu. By measuring the amount of work completed by the thread, idleness of
each CPU can be derived accordingly.
An unit work is defined as touching a full page of unsigned
characters. Mean and standard deviation of time to complete an unit work is
reported in "unit work" section. Options can be chosen to report
detailed percpu idleness or overall system idleness by aggregating percpu
stats.
Fio is usually run in one of two ways, when data verification is
done. The first is a normal write job of some sort with verify enabled. When
the write phase has completed, fio switches to reads and verifies everything
it wrote. The second model is running just the write phase, and then later
on running the same job (but with reads instead of writes) to repeat the
same I/O patterns and verify the contents. Both of these methods depend on
the write phase being completed, as fio otherwise has no idea how much data
was written.
With verification triggers, fio supports dumping the current write
state to local files. Then a subsequent read verify workload can load this
state and know exactly where to stop. This is useful for testing cases where
power is cut to a server in a managed fashion, for instance.
A verification trigger consists of two things:
1) Storing the write state of each job.
2) Executing a trigger command.
The write state is relatively small, on the order of hundreds of
bytes to single kilobytes. It contains information on the number of
completions done, the last X completions, etc.
A trigger is invoked either through creation ('touch') of a
specified file in the system, or through a timeout setting. If fio is run
with `--trigger-file=/tmp/trigger-file', then it will continually check for
the existence of `/tmp/trigger-file'. When it sees this file, it will fire
off the trigger (thus saving state, and executing the trigger command).
For client/server runs, there's both a local and remote trigger.
If fio is running as a server backend, it will send the job states back to
the client for safe storage, then execute the remote trigger, if specified.
If a local trigger is specified, the server will still send back the write
state, but the client will then execute the trigger.
Verification trigger example
Let's say we want to run a powercut test on the remote
Linux machine 'server'. Our write workload is in `write-test.fio'. We want to
cut power to 'server' at some point during the run, and we'll run this test
from the safety or our local machine, 'localbox'. On the server, we'll start
the fio backend normally:
and on the client, we'll fire off the workload:
localbox$ fio --client=server --trigger-file=/tmp/my-trigger
--trigger-remote="bash -c "echo b >
/proc/sysrq-triger""
We set `/tmp/my-trigger' as the trigger file, and we tell fio to
execute:
echo b > /proc/sysrq-trigger
on the server once it has received the trigger and sent us the
write state. This will work, but it's not really cutting power to the
server, it's merely abruptly rebooting it. If we have a remote way of
cutting power to the server through IPMI or similar, we could do that
through a local trigger command instead. Let's assume we have a script that
does IPMI reboot of a given hostname, ipmi-reboot. On localbox, we could
then have run fio with a local trigger instead:
localbox$ fio --client=server --trigger-file=/tmp/my-trigger
--trigger="ipmi-reboot server"
For this case, fio would wait for the server to send us the write
state, then execute `ipmi-reboot server' when that happened.
Loading verify state
To load stored write state, a read verification job file
must contain the verify_state_load option. If that is set, fio will
load the previously stored state. For a local fio run this is done by loading
the files directly, and on a client/server run, the server backend will ask
the client to send the files over and load them from there.
Fio supports a variety of log file formats, for logging latencies,
bandwidth, and IOPS. The logs share a common format, which looks like
this:
time (msec), value, data direction, block size (bytes), offset
(bytes)
`Time' for the log entry is always in milliseconds. The `value'
logged depends on the type of log, it will be one of the following:
`Data direction' is one of the following:
- 0
- I/O is a READ
- 1
- I/O is a WRITE
- 2
- I/O is a TRIM
The entry's `block size' is always in bytes. The `offset' is the
position in bytes from the start of the file for that particular I/O. The
logging of the offset can be toggled with log_offset.
Fio defaults to logging every individual I/O but when windowed
logging is set through log_avg_msec, either the average (by default)
or the maximum (log_max_value is set) `value' seen over the specified
period of time is recorded. Each `data direction' seen within the window
period will aggregate its values in a separate row. Further, when using
windowed logging the `block size' and `offset' entries will always contain
0.
Normally fio is invoked as a stand-alone application on the
machine where the I/O workload should be generated. However, the backend and
frontend of fio can be run separately i.e., the fio server can generate an
I/O workload on the "Device Under Test" while being controlled by
a client on another machine.
Start the server on the machine which has access to the storage
DUT:
where `args' defines what fio listens to. The arguments are of the
form `type,hostname' or `IP,port'. `type' is either `ip' (or ip4) for TCP/IP
v4, `ip6' for TCP/IP v6, or `sock' for a local unix domain socket.
`hostname' is either a hostname or IP address, and `port' is the port to
listen to (only valid for TCP/IP, not a local socket). Some examples:
- 1) fio --server
- Start a fio server, listening on all interfaces on the default port
(8765).
- 2) fio --server=ip:hostname,4444
- Start a fio server, listening on IP belonging to hostname and on port
4444.
- 3) fio --server=ip6:::1,4444
- Start a fio server, listening on IPv6 localhost ::1 and on port 4444.
- 4) fio --server=,4444
- Start a fio server, listening on all interfaces on port 4444.
- 5) fio --server=1.2.3.4
- Start a fio server, listening on IP 1.2.3.4 on the default port.
- 6) fio --server=sock:/tmp/fio.sock
- Start a fio server, listening on the local socket `/tmp/fio.sock'.
Once a server is running, a "client" can connect to the
fio server with:
$ fio <local-args> --client=<server>
<remote-args> <job file(s)>
where `local-args' are arguments for the client where it is
running, `server' is the connect string, and `remote-args' and `job file(s)'
are sent to the server. The `server' string follows the same format as it
does on the server side, to allow IP/hostname/socket and port strings.
Fio can connect to multiple servers this way:
$ fio --client=<server1> <job file(s)>
--client=<server2> <job file(s)>
If the job file is located on the fio server, then you can tell
the server to load a local file as well. This is done by using
--remote-config:
$ fio --client=server --remote-config /path/to/file.fio
Then fio will open this local (to the server) job file instead of
being passed one from the client.
If you have many servers (example: 100 VMs/containers), you can
input a pathname of a file containing host IPs/names as the parameter value
for the --client option. For example, here is an example `host.list'
file containing 2 hostnames:
host1.your.dns.domain
host2.your.dns.domain
The fio command would then be:
$ fio --client=host.list <job file(s)>
In this mode, you cannot input server-specific parameters or job
files -- all servers receive the same job file.
In order to let `fio --client' runs use a shared filesystem from
multiple hosts, `fio --client' now prepends the IP address of the server to
the filename. For example, if fio is using the directory `/mnt/nfs/fio' and
is writing filename `fileio.tmp', with a --client `hostfile'
containing two hostnames `h1' and `h2' with IP addresses 192.168.10.120 and
192.168.10.121, then fio will create two files:
/mnt/nfs/fio/192.168.10.120.fileio.tmp
/mnt/nfs/fio/192.168.10.121.fileio.tmp
fio was written by Jens Axboe <axboe@kernel.dk>.
This man page was written by Aaron Carroll <aaronc@cse.unsw.edu.au>
based on documentation by Jens Axboe.
This man page was rewritten by Tomohiro Kusumi <tkusumi@tuxera.com>
based on documentation by Jens Axboe.
Report bugs to the fio mailing list
<fio@vger.kernel.org>.
See REPORTING-BUGS.
REPORTING-BUGS:
http://git.kernel.dk/cgit/fio/plain/REPORTING-BUGS
For further documentation see HOWTO and README.
Sample jobfiles are available in the `examples/' directory.
These are typically located under `/usr/share/doc/fio'.
HOWTO: http://git.kernel.dk/cgit/fio/plain/HOWTO
README: http://git.kernel.dk/cgit/fio/plain/README