pcp-tapestat1

Usage

Overview

pcp-tapestat reports I/O statistics for tape devices.

Options

When invoked via the pcp(1) command, the pcp options -A/ --align, -a/ --archive, -h/ --host, -O/ --origin, -S/ --start, -s/ --samples, -t/ --interval, -T/ --finish, -V/ --version, -Z/ --timezone and -z/ --hostzone 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.

-V, --version

Display version number and exit.

-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.

-?, --help

Display usage message and exit.

Report

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 environment

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).

Options

The -D or --debug pcp option enables the output of additional diagnostics on stderr to help triage problems, although the information is sometimes cryptic and primarily intended to provide guidance for developers rather than for end-users. debug is a comma separated list of debugging options; use pmdbg(1) with the -l option to obtain a list of the available debugging options and their meaning.