NAME¶
pmiostat - performance metrics value dumper
SYNOPSIS¶
pmiostat [
-A align --align=TIME] [
-a
archive --archive=FILE] [
-h host
--host= HOST] [
-O offset
--origin=TIME] [
-S starttime
--start=TIME] [
-s samples
--samples=N] [
-T endtime
--finish=TIME] [
-t interval
--interval=DELTA] [
-Z timezone
--timezone=TZ] [
-z --hostzone] [
-?
--help] [
-x [dm][,t][,h]]
DESCRIPTION¶
pmiostat reports I/O statistics for scsi devices (by default) or
device-mapper devices (if the
-x dm option is specified). By default
pmiostat 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
pmiostat are as follows:
- -a
- Performance metric values are retrieved from the Performance Co-Pilot
(PCP) archive log file identified by the base name archive.
- -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,
pmiostat will sample and report continuously (in real time mode) or
until the end of the PCP archive (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 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.
- -Z
- By default, pmiostat reports the time of day according to the local
timezone on the system where pmiostat is run. The -Z option
changes the timezone to timezone in the format of the environment
variable TZ as described in environ(5).
- -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.
- -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.
REPORT¶
The columns in the
pmiostat 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.
- 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).
SEE ALSO¶
PCPIntro(1),
pmcd(1),
pmchart(1),
pmdumplog(1),
pminfo(1),
pmlogger(1),
pmtime(1),
PMAPI(3),
__pmSpecLocalPMDA(3),
pcp.conf(5) and
pcp.env(5).
DIAGNOSTICS¶
All are generated on standard error and are intended to be
self-explanatory.