Ubuntu Manpage: pmiostat, pcp-iostat - performance metrics i/o statistics tool

NAME

       pmiostat, pcp-iostat - performance metrics i/o statistics tool

SYNOPSIS

       pcp iostat  [-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 [dm][,t][,h][,noidle]]

DESCRIPTION

pcp-iostat reports I/O statistics for scsi devices (by default) or device-mapper devices (if the -x dm
option is specified). By default pcp-iostat 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-iostat
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 'sd(a|b)$' is specified, the device column will be sum(sd(a|b)$)
and summed statistics for sda and sdb 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. This includes the %util column, which may therefore exceed 100%
if more than one device name matches. 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-iostat 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 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. '^sd[a-zA-Z]+' will
match all device names starting with 'sd' followed by one or more alphabetic characters. e.g.
'^sd(a|b)$' will only match 'sda' and 'sdb'. e.g. 'sda$' will match 'sda' but not 'sdab'. 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-iostat reports the time of day according to the local timezone on the system where
pcp-iostat 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:
dm - report statistics for device-mapper logical devices instead of scsi devices,
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-iostat 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 scsi device name, or if -x dm is specified, the device-mapper logical device name.
When -G is specified, this is replaced by the aggregation method and regular expression - see the
-G and -R options above.

rrqm/s The number of read requests expressed as a rate per-second that were merged during the reporting
interval by the I/O scheduler.

wrqm/s The number of write requests expressed as a rate per-second that were merged during the reporting
interval by the I/O scheduler.

r/s The number of read requests completed by the device (after merges), expressed as a rate per second
during the reporting interval.

w/s The number of write requests completed by the device (after merges), expressed as a rate per
second during the reporting interval.

rkB/s The average volume of data read from the device expressed as KBytes/second during the reporting
interval.

wkB/s The average volume of data written to the device expressed as KBytes/second during the reporting
interval.

avgrq-sz
The average I/O request size for both reads and writes to the device expressed as Kbytes during
the reporting interval.

avgqu-sz
The average queue length of read and write requests to the device during the reporting interval.

await The average time in milliseconds that read and write requests were queued (and serviced) to the
device during the reporting interval.

r_await
The average time in milliseconds that read requests were queued (and serviced) to the device
during the reporting interval.

w_await
The average time in milliseconds that write requests were queued (and serviced) to the device
during the reporting interval.

%util The percentage of time during the reporting interval that the device was busy processing requests.
A value of 100% indicates device saturation.

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.

Performance Co-Pilot                                   PCP                                         PCP-IOSTAT(1)