OSF

NAME

iostat − Reports I/O statistics

SYNOPSIS

iostat [drive ...] [interval] [count]

DESCRIPTION

The iostat command iteratively reports the number of characters read and written to terminals per second, and, for each disk, the number of transfers per second, kilobytes transferred per second, and the milliseconds per average seek.  The iostat command 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, iostat counts the number of seeks and data transfer completions and the number of words transferred for each disk; for terminals collectively, iostat counts the number of input and output characters.  Also, each sixtieth of a second, iostat examines the state of each disk and makes a tally if the disk is active.  From these numbers and given the transfer rates of the devices, it is possible to determine the 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. 

If included after the interval argument, the count argument specifies the number of reports.  For example, iostat 1 10 would produce 10 reports at 1-second intervals.  You cannot specify count without interval, because the first numeric argument to iostat is assumed to be interval. 

If more than four disk drives are configured in the system, iostat displays only the first four drives.  To force iostat to display specific drives, you can supply the drive names on the command line. 

RELATED INFORMATION

Commands:  vmstat(1).