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Unix Version 7 - man page for iostat (v7 section 1M)

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IOSTAT(1M)									       IOSTAT(1M)

       iostat - report I/O statistics

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

       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
       typewriters.   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 examined 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 second 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 indicating	the  percentage  of  time
	      spent  in each of the possible configurations of 4 system states and 8 IO states (3
	      disks each active or not).

       -b     Report on the usage of IO buffers.

       /dev/mem, /unix

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