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IOSTAT(8) System Manager's Manual IOSTAT(8)

iostat — report I/O statistics

iostat [-c count] [-M core] [-N system] [-w wait] [drives]

Iostat displays kernel I/O statistics on terminal, disk and cpu operations.

The options are as follows:

Repeat the display count times. The first display is for the time since a reboot and each subsequent report is for the time period since the last display. If no wait interval is specified, the default is 1 second.
Extract values associated with the name list from the specified core instead of the default “/dev/kmem”.
Extract the name list from the specified system instead of the default “/vmunix”.
Pause wait seconds between each display. If no repeat count is specified, the default is infinity.

Iostat displays its information in the following format:

tty
tin
characters read from terminals
tout
characters written to terminals
disks
Disk operations (this field is system dependent). The header of the field is the disk name and unit number. 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, their names may be supplied on the command line.

sps
sectors transferred per second
tps
transfers per second
msps
milliseconds per average seek (including implied seeks and rotational latency)
cpu
us
% of cpu time in user mode
ni
% of cpu time in user mode running niced processes
sy
% of cpu time in system mode
id
% of cpu time in idle mode

/vmunix
Default kernel namelist.
/dev/kmem
Default memory file.

fstat(1), netstat(1), nfsstat(1), ps(1), systat(1), vmstat(1), pstat(8)

The sections starting with ``Interpreting system activity'' in Installing and Operating 4.3BSD.

BSD 4 June 6, 1993 IOSTAT(8)