iostat(1)

DESCRIPTION

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

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.

EXAMPLES

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:

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

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

SEE ALSO

vmstat(1).