NAME
iostat
—
report I/O statistics
SYNOPSIS
iostat |
[-CdDITxy ] [-c
count] [-w
wait] [drives] |
DESCRIPTION
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 forceiostat
to display specific drives, they may be supplied on the command line, either as names orfnmatch
() patterns.- KB/t
- Kilobytes transferred per disk transfer
- t/s
- transfers per second
- MB/s
- Megabytes transferred per second
-D
), presents the following values.- KB
- Kilobytes transferred
- xfr
- Disk transfers
- time
- Seconds spent in disk activity
-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
SEE ALSO
fstat(1), netstat(1), nfsstat(1), ps(1), systat(1), vmstat(1), fnmatch(3), pstat(8)
The sections starting with ``Interpreting system activity'' in Installing and Operating 4.3BSD.
HISTORY
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.