Mac OS X / Darwin man pages : iostat (8)
iostat (8)
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iostat - report I/O statistics
iostat [-CdKIoT?] [-c count] [-n devs] [-w wait] [drives]
Iostat displays kernel I/O statistics on terminal, device and cpu operations.
The first statistics that are printed are averaged over the system
uptime. To get information about the current activity, a suitable
wait time should be specified, so that the subsequent sets of printed
statistics will be averaged over that time.
The options are as follows:
- -c
- Repeat the display count times. If no wait interval is specified,
the default is 1 second.
- -C
- Display CPU statistics. This is on by default, unless -d is specified.
- -d
- Display only device statistics. If this flag is turned on, only
device statistics will be displayed, unless -C or -T is also specfied
to enable the display of CPU or TTY statistics.
- -I
- Display total statstics for a given time period, rather than average
statistics for each second during that time period.
- -K
- In the blocks transferred display (-o), display block count in
kilobytes rather then the device native block size.
- -n
- Display up to devs number of devices. iostat will display fewer
devices if there aren't devs devices present.
- -o
- Display old-style iostat device statistics. Sectors per second,
transfers per second, and miliseconds per seek are displayed. If
-I is specified, total blocks/sectors, total transfers, and
miliseconds per seek are displayed.
- -T
- Display TTY statistics. This is on by default, unless -d is specified.
- -w
- Pause wait seconds between each display. If no repeat count is
specified, the default is infinity.
- -?
- Display a usage statement and exit.
Iostat displays its information in the following format:
tty
- tin
- characters read from terminals
- tout
- characters written to terminals
devices
Device operations. The header of the field is the device name and
unit number. iostat will display as many devices as will fit in a
standard 80 column screen, or the maximum number of devices in the
system, whichever is smaller. If -n is specified on the command
line, iostat will display the smaller of the requested number of
devices, and the maximum number of devices in the system. To force
iostat to display specific drives, their names may be supplied on
the command line. iostat will not display more devices than will
fit in an 80 column screen, unless the -n argument is given on the
command line to specify a maximum number of devices to display, or
the list of specified devices exceeds 80 columns. If fewer devices
are specified on the command line than will fit in an 80 column
screen, iostat will show only the specified devices.
The standard iostat device display shows the following statistics:
- KB/t
- kilobytes per transfer
- tps
- transfers per second
- MB/s
- megabytes per second
The standard iostat device display, with the -I flag specified,
shows the following statistics:
- KB/t
- kilobytes per transfer
- xfrs
- total number of transfers
- MB
- total number of megabytes transferred
The old-style iostat display (using -o) shows the following statistics:
- sps
- sectors transferred per second
- tps
- transfers per second
- msps
- average milliseconds per transaction
The old-style iostat display, with the -I flag specified, shows the
following statistics:
- blk
- total blocks/sectors transferred
- xfr
- total transfers
- msps
- average milliseconds per transaction
cpu
- us
- % of cpu time in user mode
- sy
- % of cpu time in system mode
- id
- % of cpu time in idle mode
iostat -w 1 disk0 disk2
Display statistics for the first and third disk devices device every second
ad infinitum.
iostat -c 2
Display the statistics for the first four devices in the system twice,
with a one second display interval.
iostat -Iw 3
Display total statistics every three seconds ad infinitum.
iostat -odICTw 2 -c 9
Display total statistics using the old-style output format 9 times, with
a two second interval between each measurement/display. The -d flag generally
disables the TTY and CPU displays, but since the -T and -C flags
are given, the TTY and CPU displays will be displayed.
fstat(1)
, netstat(1)
, nfsstat(1)
, ps(1)
, pstat(8)
,
The sections starting with ``Interpreting system activity'' in Installing
and Operating 4.3BSD.
This version of iostat first appeared in FreeBSD 3.0.
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