pcp-tapestat - performance metrics i/o tape statistics
tool
pcp-tapestat [-A align
--align=TIME] [-a archive
--archive=FILE] [-G method
--aggregate=method] [-h host
--host=HOST] [-O offset
--origin=TIME] [-S starttime
--start=TIME] [-s samples
--samples=N] [-T endtime
--finish=TIME] [-t interval
--interval=DELTA] [-P precision
--precision=N] [-R pattern
--regex=pattern] [-u --no-interpolate]
[-Z timezone --timezone=TZ] [-z
--hostzone] [-? --help] [-x
[t][,h][,noidle]]
pcp-tapestat reports I/O statistics for tape devices By
default pcp-tapestat reports live data for the local host but can
also report for a remote host (-h) or from a previously captured PCP
archive (-a).
The -S, -T, -O and -A options may be
used to define a time window to restrict the samples retrieved, set an
initial origin within the time window, or specify a ``natural'' alignment of
the sample times; refer to PCPIntro(1) for a complete description of
these options.
The other options which control the source, timing and layout of
the information reported by pcp-tapestat are as follows:
- -a
- Performance metric values are retrieved from the Performance Co-Pilot
(PCP) archive log files identified by the argument archive, which
is a comma-separated list of names, each of which may be the base name of
an archive or the name of a directory containing one or more archives. See
also -u.
- -G
- Specifies that statistics for device names matching the regular expression
specified with the -R regex option should be aggregated
according to method. Note this is aggregation based on matching
device names (not temporal aggregation). When -G is used, the
device name column is reported as method(regex), e.g. if
-G sum -R 'st(0|1)$' is specified, the device column will be
sum(st(0|1)$) and summed statistics for st0 and
st1 will be reported in the remaining columns. If -G is
specified but -R is not specified, then the default regex is
.*, i.e. matching all device names. If method is sum
then the statistics are summed. If method is avg then the
statistics are summed and then averaged by dividing by the number of
matching device names. If method is min or max, the
minimum or maximum statistics for matching devices are reported,
respectfully.
- -h
- Current performance metric values are retrieved from the nominated
host machine.
- -s
- The argument samples defines the number of samples to be retrieved
and reported. If samples is 0 or -s is not specified,
pcp-tapestat will sample and report continuously (in real time
mode) or until the end of the set of PCP archives (in archive mode).
- -t
- The default update interval may be set to something other than the
default 1 second. The interval argument follows the syntax
described in PCPIntro(1), and in the simplest form may be an
unsigned integer (the implied units in this case are seconds). The
-t option is particularly useful when replaying large sets of
archives (-a option) that span several hours or even days. In this
case specifying a large interval (e.g. 1h for 1 hour) will reduce
the volume of data reported and the tape i/o statistics will be averaged
(interpolated) over the reporting interval (unless the -u option is
specified, see below).
- -R
- This restricts the report to device names matching regex. The
regex pattern is searched as a perl style regular expression, and
will match any portion of a device name. e.g. '^st[0-9]+' will match all
device names starting with 'st' followed by one or more numbers. e.g.
'^st(0|1)$' will only match 'st0' and 'st1'. e.g. 'st0$' will match 'st0'
but not 'st1'. See also the -G option for aggregation options.
- -P
- This indicates the number of decimals to print. The default precision
N may be set to something other than the default 2 decimals. Note
that the avgrq-sz and avgqu-sz fields are always reported
with N+1 decimals of precision. These fields typically have values
less than 1.0.
- -u
- When replaying a set of archives, by default values are reported according
to the selected sample interval (-t option), not according to the
actual record intervals in the set of archives. To this effect PCP
interpolates the values to be reported based on the records in the set of
archives, and is particularly useful when the -t option is used to
replay a set of archives with a longer sampling interval than the
underlying interval the set of archives was originally recorded with. With
the -u option, uninterpolated reporting is enabled - every value is
reported according to the native recording interval in the set of
archives. When the -u option is specified, the -t option
makes no sense and is incompatible because the replay interval is always
the same as the recording interval in the set of archive. In addition,
-u only makes sense when replaying a set of archives, see -a
above, and so if -u is specified then -a must also be
specified.
- -Z
- By default, pcp-tapestat reports the time of day according to the
local timezone on the system where pcp-tapestat is run. The
-Z option changes the timezone to timezone in the format of
the environment variable TZ as described in environ(7).
- -z
- Change the reporting timezone to the local timezone at the host that is
the source of the performance metrics, as identified via either the
-h or -a options. When replaying a PCP archive that was
captured in a foreign timezone, the -z option would almost always
be used (the default reporting timezone is the local timezone, which may
not be the same as the timezone of the PCP archive).
- -x
- Specifies a comma separated list of one or more extended reporting options
as follows:
t - prefix every line in the report with a timestamp in
ctime(3) format,
h - omit the heading, which is otherwise reported every 24 samples,
noidle - Do not display statistics for idle devices.
The columns in the pcp-tapestat report have the following
interpretation :
- Timestamp
- When the -x t option is specified, this column is the timestamp in
ctime(3) format.
- Device
- Specifies the tape device name When -G is specified, this is
replaced by the aggregation method and regular expression - see the
-G and -R options above.
- r/s
- The number of reads issued expressed as the number per second averaged
over the interval.
- w/s
- The number of writes issued expressed as the number per second averaged
over the interval.
- kb_r/s
- The amount of data read expressed in kilobytes per second averaged over
the interval.
- kb_w/s
- The amount of data written expressed in kilobytes per second averaged over
the interval.
- r_pct
- Read percentage wait - The percentage of time over the interval spent
waiting for read requests to complete. The time is measured from when the
request is dispatched to the SCSI mid-layer until it signals that it
completed.
- w_pct
- Write percentage wait - The percentage of time over the interval spent
waiting for write requests to complete. The time is measured from when the
request is dispatched to the SCSI mid-layer until it signals that it
completed.
- o_pct
- Overall percentage wait - The percentage of time over the interval spent
waiting for any I/O request to complete (read, write, and other).
- Rs/s
- The number of I/Os, expressed as the number per second averaged over the
interval, where a non-zero residual value was encountered.
- o_cnt
- The number of I/Os, expressed as the number per second averaged over the
interval, that were included as "other". Other I/O includes
ioctl calls made to the tape driver and implicit operations performed by
the tape driver such as rewind on close (for tape devices that implement
rewind on close). It does not include any I/O performed using methods
outside of the tape driver (e.g. via sg ioctls).
- $PCP_VAR_DIR/pmns/*
- default PMNS specification files
Environment variables with the prefix PCP_ are used to
parameterize the file and directory names used by PCP. On each installation,
the file /etc/pcp.conf contains the local values for these variables.
The $PCP_CONF variable may be used to specify an alternative
configuration file, as described in pcp.conf(5).
All are generated on standard error and are intended to be
self-explanatory.