NAME

iostat − report I/O statistics

SYNOPSIS

iostat [ interval [ count ] ]

DESCRIPTION

Iostat iteratively reports the number of characters read and written to terminals, and, for each disk, the number of seeks and transfers per second, and the milliseconds per average seek.  It also gives the percentage of time the system has spent in user mode, in user mode running low priority (niced) processes, in system mode, and idling. 

To compute this information, for each disk, seeks and data transfer completions and number of words transferred are counted; for terminals collectively, the number of input and output characters are counted.  Also, each fiftieth of a second, the state of each disk is examined and a tally is made if the disk is active.  From these numbers and given the transfer rates of the devices it is possible to determine average seek times for each device. 

The optional interval argument causes iostat to report once each interval seconds.  The first report is for  all time since a reboot and each subsequent report is for the last interval only. 

The optional count argument restricts the number of reports. 

FILES

/dev/kmem
/vmunix

SEE ALSO

vmstat(8)

Sun Release 3.0β  —  Last change: 1 February 1985