iostat(8) BSD System Manager's Manual iostat(8)
NAME
iostat -- report I/O statistics
SYNOPSIS
iostat [-CUdKIoT?] [-c count] [-n devs] [-w wait] [drives]
DESCRIPTION
Iostat displays kernel I/O statistics on terminal, device and cpu opera-
tions. The first statistics that are printed are averaged over the sys-
tem 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:
-? Display a usage statement and exit.
-C Display CPU statistics. This is on by default, unless -d is speci-
fied.
-c Repeat the display count times. If no wait interval is specified,
the default is 1 second.
-d Display only device statistics. If this flag is turned on, only
device statistics will be displayed, unless -C or -U or -T is also
specfied to enable the display of CPU, load average or TTY statis-
tics.
-I Display total statstics for a given time period, rather than aver-
age 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 speci-
fied.
-U Display system load averages. 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.
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 statis-
tics:
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
EXAMPLES
iostat -w 1 disk0 disk2
Display statistics for the first and third disk devices device every sec-
ond 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 gen-
erally disables the TTY and CPU displays, but since the -T and -C flags
are given, the TTY and CPU displays will be displayed.
SEE ALSO
fstat(1), netstat(1), nfsstat(1), ps(1), pstat(8)
The sections starting with ``Interpreting system activity'' in Installing
and Operating 4.3BSD.
HISTORY
This version of iostat first appeared in FreeBSD 3.0.
BSD September 27, 2001 BSD
Mac OS X 10.8 - Generated Tue Sep 4 05:50:00 CDT 2012