iostat(1)

NAME

iostat — report I/O statistics

SYNOPSIS

iostat [-t] [-L] [interval [count]]

DESCRIPTION

iostat iteratively reports I/O statistics for each active disk on the system. Disk data is arranged in a four-column format:

Column Heading	`Interpretation`
`device`	Device name
`bps`	Kilobytes transferred per second
`sps`	Number of seeks per second
`msps`	Milliseconds per average seek

If two or more disks are present, data is presented on successive lines for each disk.

To compute this information, seeks, data transfer completions, and the number of words transferred are counted for each disk. Also, the state of each disk is examined HZ times per second (as defined in <sys/param.h>) and a tally is made if the disk is active. These numbers can be combined with the transfer rates of each device to determine average seek times for each device.

With the advent of new disk technologies, such as data striping, where a single data transfer is spread across several disks, the number of milliseconds per average seek becomes impossible to compute accurately. At best it is only an approximation, varying greatly, based on several dynamic system conditions. For this reason and to maintain backward compatibility, the milliseconds per average seek (msps) field is set to the value 1.0.

Options

iostat recognizes the following options and command-line arguments:

-t

Report terminal statistics as well as disk (or lunpath) statistics. When used with the -L option, lunpath and terminal statistics are displayed. Terminal statistics include:

tin: Number of characters read from terminals.
tout: Number of characters written to terminals.
us: Percentage of time system (active processors) has spent in user mode.
ni: Percentage of time system (active processors) has spent in user mode running low-priority (nice) processes.
sy: Percentage of time system (active processors) has spent in system mode.
id: Percentage of time system (active processors) has spent idling.

interval

Display successive lines which are summaries of the last interval seconds. The first line reported is for the time since a reboot and each subsequent line is for the last interval only.

count

Repeat the statistics count times.

-L

Report active lunpath statistics. When used with the -t option, lunpath and terminal statistics are reported. The lunpaths are not displayed in any specific order, and the current order may change in future releases. Lunpath data is arranged in a four-column format:

lunpath

symbolic name of the lunpath of the form: diskm_lunpath n, where m is the instance number of LUN and n is the instance number of lunpath. For example, in disk47_lunpath7, m is 47 and n is 7. These instance numbers are displayed by ioscan using the -N option for the LUN and lunpath entries. For more information on LUN and lunpath hardware path, refer to intro(7).

bps

Kilobytes transferred per second.

sps

Number of seeks per second.

msps

Milliseconds per average seek.

For multiple lunpaths, data is presented on successive lines for each active lunpath. If no lunpaths were active, a blank line is printed.

EXAMPLES

Show current I/O statistics for all disks:

iostat

Display I/O statistics for all disks every 10 seconds until INTERRUPT or QUIT is pressed:

iostat 10 

Display I/O statistics for all disks every 10 seconds and terminate after 5 successive readings:

iostat 10 5 

Display I/O statistics for all disks every 10 seconds, also show terminal and processor statistics, and terminate after 5 successive readings:

iostat -t 10 5 

Display I/O statistics for all active lunpaths:

iostat -L 

Display I/O statistics for all active lunpaths every 10 seconds until INTERRUPT or QUIT is pressed:

iostat -L 10 

Display I/O statistics for all active lunpaths every 10 seconds, and terminate after 5 successive readings:

iostat -L 10 5 

Display I/O statistics for all active lunpaths every 10 seconds, also show terminal and processor statistics, and terminate after 5 successive readings:

iostat -L -t 10 5 

WARNINGS

Users of iostat must not rely on the exact field widths and spacing of its output, as these will vary depending on the system, the release of HP-UX, and the data to be displayed.

AUTHOR

iostat was developed by the University of California, Berkeley, and HP.

FILES

/usr/include/sys/param.h

iostat(1)

Technical documentation

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