iostat.1 (2010 09)

i
iostat(1) 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 accu-
rately. 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 _lunpathn, 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.
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1