Ubuntu Manpage: pcp-tapestat - performance metrics i/o tape statistics tool

NAME

       pcp-tapestat - performance metrics i/o tape statistics tool

SYNOPSIS

       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]]

DESCRIPTION

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.

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).

FILES

       $PCP_VAR_DIR/pmns/*
                 default PMNS specification files

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).

DIAGNOSTICS

       All are generated on standard error and are intended to be self-explanatory.