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


     iostat - report I/O statistics


     iostat [-CDdIT] [-c count] [-M core] [-N system] [-w wait] [drives]


     iostat displays kernel I/O statistics on terminal, disk and CPU
     operations.  By default, iostat displays one line of statistics averaged
     over the machine's run time.  The -I option causes iostat to print raw,
     unaveraged values.

     The options are as follows:

     -C      Show CPU statistics.  This is enabled by default unless the -D,
             -d, or -T flags are used.

     -c count
             Repeat the display count times.  Unless the -I flag is in effect,
             the first display is for the time since a reboot and each
             subsequent report is for the time period since the last display.
             Unless overridden by the -w option, the wait interval between
             lines is 1 second.

     -D      Show alternate disk statistics.  Displays kilobytes transferred,
             number of transfers, and time spent in transfers.  Use of this
             flag disables the default display.

     -d      Show disk statistics.  This is the default.  Displays kilobytes
             per transfer, number of transfers, and megabytes transferred.
             Use of this flag disables display of CPU and tty statistics.

     -I      Show the running total values, rather than an average.

     -M core
             Extract values associated with the name list from the specified
             core instead of the default /dev/mem.

     -N system
             Extract the name list from the specified system instead of the
             default "/bsd".

     -T      Show tty statistics.  This is enabled by default unless the -C,
             -D, or -d flags are used.

     -w wait
             Pause wait seconds between each display.  Unless a count is
             specified via the -c option, iostat will display output until it
             is interrupted.

     iostat displays its information in the following format:

           tin     characters read from terminals
           tout    characters written to terminals

           Disk operations.  The header of the field is the disk name and unit
           number.  If more than four disk drives are configured in the
           system, iostat displays only the first four drives.  To force
           iostat to display specific drives, their names may be supplied on
           the command line.

           KB/t    Kilobytes transferred per disk transfer
           t/s     Transfers per second
           MB/s    Megabytes transferred per second
           The alternate display format, (selected with -D), presents the
           following values:

           KB      Kilobytes transferred
           xfr     Disk transfers
           time    Seconds spent in disk activity

           us      % of CPU time in user mode
           ni      % of CPU time in user mode running niced processes
           sy      % of CPU time in system mode
           sp      % of CPU time spent spinning
           in      % of CPU time processing interrupts
           id      % of CPU time in idle mode


     /bsd      default kernel namelist
     /dev/mem  default memory file


     fstat(1), netstat(1), nfsstat(1), ps(1), systat(1), top(1), pstat(8),

     The sections starting with "Interpreting system activity" in Installing
     and Operating 4.3BSD.

OpenBSD 6.4                    September 7, 2018                   OpenBSD 6.4

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