iostat
Manual Reference Pages - IOSTAT (1)
NAME
iostat - Report Central Processing Unit (CPU) statistics and input/output statistics for devices and partitions.
CONTENTS
Synopsis
Description
Reports
Options
Environment
Examples
Bugs
Files
Author
See Also
SYNOPSIS
iostat [ -c | -d ] [ -k | -m ] [ -t ] [ -V ] [ -x ] [ device [ ... ] | ALL ] [ -p [ device | ALL ] ] [ interval [ count ] ]
DESCRIPTION
The iostat command is used for monitoring system input/output device loading by observing the time the devices are active in relation to their average transfer rates. The iostat command generates reports that can be used to change system configuration to better balance the input/output load between physical disks.
The first report generated by the iostat command provides statistics concerning the time since the system was booted. Each subsequent report covers the time since the previous report. All statistics are reported each time the iostat command is run. The report consists of a CPU header row followed by a row of CPU statistics. On multiprocessor systems, CPU statistics are calculated system-wide as averages among all processors. A device header row is displayed followed by a line of statistics for each device that is configured.
The interval parameter specifies the amount of time in seconds between each report. The first report contains statistics for the time since system startup (boot). Each subsequent report contains statistics collected during the interval since the previous report. The count parameter can be specified in conjunction with the interval parameter. If the count parameter is specified, the value of count determines the number of reports generated at interval seconds apart. If the interval parameter is specified without the count parameter, the iostat command generates reports continuously.
REPORTS
The iostat command generates two types of reports, the CPU Utilization report and the Device Utilization report.
CPU Utilization Report |
The first report generated by the
iostat command is the CPU
Utilization Report. For multiprocessor systems, the CPU values are
global averages among all processors.
The report has the following format:
%user
%nice
%system
%iowait
%steal
%idle
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Device Utilization Report |
The second report generated by the
iostat command is the Device Utilization
Report. The device report provides statistics on a per physical device
or partition basis. Block devices for which statistics are to be displayed
may be entered on the command line. Partitions may also be entered on the
command line providing that option -x is not used.
If no device nor partition
is entered, then statistics are displayed
for every device used by the system, and
providing that the kernel maintains statistics for it.
If the
ALL keyword is given on the command line, then statistics are
displayed for every device defined by the system, including those
that have never been used.
The report may show the following fields,
depending on the flags used:
Device:
tps
Blk_read/s
Blk_wrtn/s
Blk_read
Blk_wrtn
kB_read/s
kB_wrtn/s
kB_read
kB_wrtn
MB_read/s
MB_wrtn/s
MB_read
MB_wrtn
rrqm/s
wrqm/s
r/s
w/s
rsec/s
wsec/s
rkB/s
wkB/s
rMB/s
wMB/s
avgrq-sz
avgqu-sz
await
svctm
%util
|
OPTIONS
-c | The -c option is exclusive of the -d option and displays only the CPU usage report. |
-d | The -d option is exclusive of the -c option and displays only the device utilization report. |
-k | Display statistics in kilobytes per second instead of blocks per second. Data displayed are valid only with kernels 2.4 and newer. |
-m | Display statistics in megabytes per second instead of blocks or kilobytes per second. Data displayed are valid only with kernels 2.4 and newer. |
-p [ { device | ALL } ] | The -p option is exclusive of the -x option and displays statistics for block devices and all their partitions that are used by the system. If a device name is entered on the command line, then statistics for it and all its partitions are displayed. Last, the ALL keyword indicates that statistics have to be displayed for all the block devices and partitions defined by the system, including those that have never been used. Note that this option works only with post 2.5 kernels. |
-t | Print the time for each report displayed. |
-V | Print version number then exit. |
-x | Display extended statistics. This option is exclusive of the -p one, and works with post 2.5 kernels since it needs /proc/diskstats file or a mounted sysfs to get the statistics. This option may also work with older kernels (e.g. 2.4) only if extended statistics are available in /proc/partitions (the kernel needs to be patched for that). |
ENVIRONMENT
The iostat command takes into account the following environment variable:
S_TIME_FORMAT | If this variable exists and its value is ISO then the current locale will be ignored when printing the date in the report header. The iostat command will use the ISO 8601 format (YYYY-MM-DD) instead. |
EXAMPLES
iostat
Display a single history since boot report for all CPU and Devices.
iostat -d 2
Display a continuous device report at two second intervals.
iostat -d 2 6
Display six reports at two second intervals for all devices.
iostat -x hda hdb 2 6
Display six reports of extended statistics at two second intervals for devices hda and hdb.
iostat -p sda 2 6
Display six reports at two second intervals for device sda and all its partitions (sda1, etc.)
BUGS
/proc filesystem must be mounted for iostat to work.
Extended statistics are available only with post 2.5 kernels.
FILES
/proc/stat contains system statistics.
/proc/partitions contains disk statistics (for pre 2.5 kernels that have been patched).
/proc/diskstats contains disks statistics (for post 2.5 kernels).
/sys contains statistics for block devices (post 2.5 kernels).
AUTHOR
Sebastien Godard (sysstat <at> wanadoo.fr)
SEE ALSO
http://perso.orange.fr/sebastien.godard/
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