iostat
—
report I/O statistics
iostat |
[-CdDITxy ] [-c
count] [-w
wait] [drives] |
iostat
displays kernel I/O statistics on terminal, disk
and CPU operations. By default, iostat
displays one
line of statistics averaged over the machine's run time. The use of
-c
presents successive lines averaged over the
wait period. The -I
option
causes iostat
to print raw, unaveraged values.
Only the last disk option specified (-d
,
-D
, or -x
) is used.
The options are as follows:
-c
count
- 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. If no wait interval is
specified, the default is 1 second.
-C
- Show CPU statistics. This is enabled by default unless the
-d
, -D
,
-T
, or -x
flags are
used.
-d
- 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.
-D
- Show alternative disk statistics. Displays kilobytes transferred, number
of transfers, and time spent in transfers. Use of this flag disables the
default display.
-I
- Show the running total values, rather than an average.
-T
- Show tty statistics. This is enabled by default unless the
-C
, -d
, or
-D
flags are used.
-w
wait
- Pause wait seconds between each display. If no
repeat count is specified, the default is
infinity.
-x
- Show extended disk statistics. Each disk is displayed on a line of its own
with all available statistics. This option overrides all other display
options, and all disks are displayed unless specific disks are provided as
arguments. Additionally, separate read and write statistics are
displayed.
-y
- Shows the extended statistics and additional queuing statistics.
iostat
displays its information in the
following format:
- tty
-
- tin
- characters read from terminals
- tout
- characters written to terminals
- disks
- Disk operations. The header of the field is the disk name and unit number.
If more drives are configured in the system that fit across the current
display,
iostat
displays only those drives that
fit on the display. To force iostat
to display
specific drives, they may be supplied on the command line, either as names
or fnmatch
() patterns.
- KB/t
- Kilobytes transferred per disk transfer
- t/s
- transfers per second
- MB/s
- Megabytes transferred per second
The alternative display format, (selected with -D
),
presents the following values.
- KB
- Kilobytes transferred
- xfr
- Disk transfers
- time
- Seconds spent in disk activity
With the -y
flag, the following queuing measurements
are added
- wait
- Number of I/O requests queued up
- actv
- Number of currently active I/O requests
- wsvc_t
- Average waiting time of an I/O request in milliseconds
- asvc_t
- Average duration of an I/O request in milliseconds
- wtime
- Seconds spent in the waiting queue. Queuing data might not be
available from all drivers and is then shown as zeros.
- 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
- in
- % of CPU time in interrupt mode
- id
- % of CPU time in idle mode
iostat
appeared in Version 6
AT&T UNIX. The -x
option was added in
NetBSD 1.4. Collection of queueing values and the
-y
option were added in NetBSD
8.0.