pcp-tapestat - report tape I/O statistics
pcp [pcp options] tapestat [-u]
[-G method] [-P precision] [-R
pattern] [-x [t][,h][,noidle]]
pcp-tapestat reports I/O statistics for tape devices.
When invoked via the pcp(1) command, the
-a/--archive, -h/--host,
-O/--origin, -s/--samples,
-t/--interval, -Z/--timezone and several other
pcp options become indirectly available; refer to PCPIntro(1)
for a complete description of these options.
The additional command line options available for
pcp-tapestat are:
- -G method,
--aggregate=method
- 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,
respectively.
- -P N,
--precision=N
- This indicates the precision (number of decimal places) to report. The
default precision N may be set to something other than the default
(2). 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.
- -R pattern,
--regex=pattern
- This restricts the report to device names matching a regular expression
pattern. The given 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.
- -u,
--no-interpolation
- When replaying a set of archives, by default values are reported according
to the requested sample interval (-t option), not according to the
actual interval recorded in the archive(s). Without this option PCP
interpolates the values to be reported based on the records in the set of
archives, which is particularly useful when the -t option is used
to replay a set of archives with a longer sampling interval than that with
which the archive(s) 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 archives, see the -a option on
PCPIntro(1), and so if -u is specified then -a must
also be specified.
- -x
comma-separated-options
- 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).
All are generated on standard error and are intended to be
self-explanatory.
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).
For environment variables affecting PCP tools, see
pmGetOptions(3).