# 2.11BSD#431 - /usr/man/cat1/iostat.0

    IOSTAT(1)	    UNIX Programmer's Manual		IOSTAT(1)

    NAME
         iostat - report I/O statistics

    SYNOPSIS
         iostat [ drives ] [ interval [ count ] ]

    DESCRIPTION
         Iostat iteratively reports the number of characters read and
         written to terminals per second, and, for each disk, the
         number of transfers per second, kilobytes transferred per
         second, and the milliseconds per average seek.  It also
         gives the percentage of time the system has spent in user
         mode, in user mode running low priority (niced) processes,
         in system mode, and idling.

         To compute this information, for each disk, seeks and data
         transfer completions and number of words transferred are
         counted; for terminals collectively, the number of input and
         output characters are counted.  Also, each sixtieth of a
         second, the state of each disk is examined and a tally is
         made if the disk is active.  From these numbers and given
         the transfer rates of the devices it is possible to deter-
         mine average seek times for each device.

         The optional interval argument causes iostat to report once
         each interval seconds.  The first report is for  all time
         since a reboot and each subsequent report is for the last
         interval only.

         The optional count argument restricts the number of reports.

         If more than 4 disk drives are configured in the system,
         iostat displays only the first 4 drives, with priority given
         to Massbus disk drives (i.e. if both Unibus and Massbus
         drives are present and the total number of drives exceeds 4,
         then some number of Unibus drives will not be displayed in
         favor of the Massbus drives).  To force iostat to display
         specific drives, their names may be supplied on the command
         line.

    FILES
         /dev/kmem
         /vmunix

    SEE ALSO
         vmstat(1)

    Printed 11/26/99	 April 29, 1985                         1

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