Ubuntu Manpage: pmiostat, pcp-iostat - report block I/O statistics

NAME

       pmiostat, pcp-iostat - report block I/O statistics

SYNOPSIS

       pcp [pcp options] iostat [-u] [-G method] [-P precision] [-R pattern] [-x [dm][,t][,h][,noidle]]

DESCRIPTION

       pcp-iostat reports I/O statistics for SCSI (by default) or other devices (if the -x option is specified).

OPTIONS

When invoked via the pcp(1) command, the -a/--archive, -h/--host, -O/--origin, -s/--samples,
-t/--interval, -Z/--timezone and several other pcp options become indirectly available; refer to
PCPIntro(1) for a complete description of these options.

The additional command line options available for pcp-iostat 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 '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, 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.
'^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.

-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.

-x comma-separated-options
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.

DIAGNOSTICS

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

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).