report I/O statistics
displays kernel I/O statistics on terminal, disk
and CPU operations. By default,
line of statistics averaged over the machine's run time. The
print raw, unaveraged values.
The options are as follows:
- Show CPU statistics. This is enabled by default unless the
-T flags are used.
- Repeat the display count times. Unless the
-I flag is in effect, the first display is for the
time since a reboot and each subsequent report is for the time period
since the last display. Unless overridden by the
-w option, the wait interval between lines is 1
- Show alternate disk statistics. Displays kilobytes transferred, number of
transfers, and time spent in transfers. Use of this flag disables the
- Show disk statistics. This is the default. Displays kilobytes per
transfer, number of transfers, and megabytes transferred. Use of this flag
disables display of CPU and tty statistics.
- Show the running total values, rather than an average.
- Extract values associated with the name list from the specified
core instead of the default
- Extract the name list from the specified system
instead of the default “/bsd”.
- Show tty statistics. This is enabled by default unless the
-d flags are used.
- Pause wait seconds between each display. Unless a
count is specified via the
display output until it is interrupted.
iostat displays its information in the
- characters read from terminals
- characters written to terminals
- Disk operations. 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
iostat to display specific drives, their
names may be supplied on the command line.
The alternate display format, (selected with
- Kilobytes transferred per disk transfer
- Transfers per second
- Megabytes transferred per second
presents the following values:
- Kilobytes transferred
- Disk transfers
- Seconds spent in disk activity
- % of CPU time in user mode
- % of CPU time in user mode running niced processes
- % of CPU time in system mode
- % of CPU time processing interrupts
- % of CPU time in idle mode
- default kernel namelist
- default memory file
The sections starting with “Interpreting system
activity” in Installing and Operating