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OpenDarwin 7.2.1 - man page for iostat (opendarwin section 8)

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IOSTAT(8)			   BSD System Manager's Manual				IOSTAT(8)

NAME
     iostat -- report I/O statistics

SYNOPSIS
     iostat [-CdKIoT?] [-c count] [-n devs] [-w wait] [drives]

DESCRIPTION
     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 speci-
	   fied 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 statis-
	   tics:

	   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 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 inter-
     val between each measurement/display.  The -d flag generally disables the TTY and CPU dis-
     plays, 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
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