iostat(1)                                                         iostat(1)

NAME
     iostat - report I/O statistics

SYNOPSIS

     iostat [-t] [interval [count]]

DESCRIPTION
     iostat iteratively reports I/O statistics for each active disk on the
     system.  Disk data is arranged in a four-column format:

          Column Heading           Interpretation
             device                Device name
             bps                   Kilobytes transferred per second
             sps                   Number of seeks per second
             msps                  Milliseconds per average seek

     If two or more disks are present, data is presented on successive
     lines for each disk.

     To compute this information, seeks, data transfer completions, and the
     number of words transferred are counted for each disk.  Also, the
     state of each disk is examined HZ times per second (as defined in
     <sys/param.h>) and a tally is made if the disk is active.  These
     numbers can be combined with the transfer rates of each device to
     determine average seek times for each device.

     With the advent of new disk technologies, such as data striping, where
     a single data transfer is spread across several disks, the number of
     milliseconds per average seek becomes impossible to compute
     accurately. At best it is only an approximation, varying greatly,
     based on several dynamic system conditions.  For this reason and to
     maintain backward compatibility, the milliseconds per average seek (
     msps ) field is set to the value 1.0.

   Options
     iostat recognizes the following options and command-line arguments:

          -t          Report terminal statistics as well as disk
                      statistics.  Terminal statistics include:

                           tin    Number of characters read from terminals.

                           tout   Number of characters written to
                                  terminals.
                           us     Percentage of time system has spent in
                                  user mode.
                           ni     Percentage of time system has spent in
                                  user mode running low-priority (nice)
                                  processes.
                           sy     Percentage of time system has spent in
                                  system mode.
                           id     Percentage of time system has spent
                                  idling.


          interval    Display successive lines which are summaries of the
                      last interval seconds.  The first line reported is
                      for the time since a reboot and each subsequent line
                      is for the last interval only.

          count       Repeat the statistics count times.

EXAMPLES
     Show current I/O statistics for all disks:

          iostat

     Display I/O statistics for all disks every 10 seconds until INTERRUPT
     or QUIT is pressed:

          iostat 10

     Display I/O statistics for all disks every 10 seconds and terminate
     after 5 successive readings:

          iostat 10 5

     Display I/O statistics for all disks every 10 seconds, also show
     terminal and processor statistics, and terminate after 5 successive
     readings:

          iostat -t 10 5

WARNINGS
     Users of iostat must not rely on the exact field widths and spacing of
     its output, as these will vary depending on the system, the release of
     HP-UX, and the data to be displayed.

AUTHOR
     iostat was developed by the University of California, Berkeley, and
     HP.

FILES
      /usr/include/sys/param.h

SEE ALSO
      vmstat(1).