iostat - report I/O statistics
iostat [-t] [interval [count]]
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.
iostat recognizes the following options and command-line arguments:
-t Report terminal statistics as well as disk
statistics. Terminal statistics include:
tin Number of characters read from terminals.
tout Number of characters written to
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.
Hewlett-Packard Company - 1 - HP-UX Release 11i: November 2000
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.
Show current I/O statistics for all disks:
Display I/O statistics for all disks every 10 seconds until INTERRUPT
or QUIT is pressed:
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
iostat -t 10 5
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.
iostat was developed by the University of California, Berkeley, and
Hewlett-Packard Company - 2 - HP-UX Release 11i: November 2000