pmiostat - Online in the Cloud

PROGRAM:

NAME

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

SYNOPSIS

pcp iostat [-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

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 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, pcp-iostat 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, 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.

-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 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.

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.

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