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     IOSTAT(1M)                                             IOSTAT(1M)

     NAME
          iostat - report I/O statistics

     SYNOPSIS
          iostat [ option ] ...  [ interval [ count ] ]

     DESCRIPTION
          Iostat delves into the system and reports certain statistics
          kept about input-output activity.  Information is kept about
          up to three different disks (RF, RK, RP) and about typewrit-
          ers.  For each disk, IO completions and number of words
          transferred are counted; for typewriters collectively, the
          number of input and output characters are counted.  Also,
          each sixtieth of a second, the state of each disk is exam-
          ined and a tally is made if the disk is active.  The tally
          goes into one of four categories, depending on whether the
          system is executing in user mode, in `nice' (background)
          user mode, in system mode, or idle.  From all these numbers
          and from the known transfer rates of the devices it is pos-
          sible to determine information such as the degree of IO
          overlap and 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.

          With no option argument iostat reports for each disk the
          number of transfers per minute, the milliseconds per average
          seek, and the milliseconds per data transfer exclusive of
          seek time.  It also gives the percentage of time the system
          has spend in each of the four categories mentioned above.

          The following options are available:

          -t   Report the number of characters of terminal IO per sec-
               ond as well.

          -i   Report the percentage of time spend in each of the four
               categories mentioned above, the percentage of time each
               disk was active (seeking or transferring), the percent-
               age of time any disk was active, and the percentage of
               time spent in `IO wait:' idle, but with a disk active.

          -s   Report the raw timing information: 32 numbers indicat-
               ing the percentage of time spent in each of the possi-
               ble configurations of 4 system states and 8 IO states
               (3 disks each active or not).

     IOSTAT(1M)                                             IOSTAT(1M)

          -b   Report on the usage of IO buffers.

     FILES
          /dev/mem, /unix