iostat - Reports I/O statistics
iostat [drive...] [interval] [count]
The iostat command reports the following information: For terminals (collectively), the number of characters read and written per second. For each disk, the number of transfers per second, bytes transferred per second (in kilobytes), and the milliseconds per average seek. Not all disk drives report seek times. For the system, the percentage of time the system has spent in user mode, in user mode running low priority (nice) processes, in system mode, and idling.
To compute this information,
counts the number
of seeks and data transfer completions, the number of words transferred for
each disk, and the collective number of input and output characters for terminals.
Also, each sixtieth of a second,
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.
Forces iostat to display specific drives. If drive is not specified, iostat displays the first four drives (even if more than four disk drives are configured in the system). 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. 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.
The output from this example displays cpu, terminal, and disk statistics for the first four disks on the system providing 5 reports in 1 second intervals.
# iostat 1 5
tty rz1 rz2 rz3 rz4 cpu
tin tout bps tps bps tps bps tps bps tps us ni sy id
1 52 2 0 1 0 13 1 4 1 8 0 9 83
1 16 7 1 2 0 5 2 2 0 3 0 10 87
0 0 0 0 0 0 0 0 0 0 0 0 1 98
2 2 2 1 0 0 50 6 0 0 9 0 9 82
1 191 2 1 0 0 47 6 0 0 8 0 9 83
Note that this example does not show the average seek times (msps) for
the disk drives. Not all disk drives report seek time.