NAME
       iostat - Report Central Processing Unit (CPU) statistics and input/output statistics for devices and partitions.

OPTIONS
       -c     The -c option is exclusive of the -d option and displays only the CPU usage report.

       -d     The -d option is exclusive of the -c option and displays only the device utilization report.

       -k     Display statistics in kilobytes per second instead of blocks per second.  Data displayed are valid only with kernels 2.4 and newer.

       -m     Display statistics in megabytes per second instead of blocks or kilobytes per second.  Data displayed are valid  only  with  kernels  2.4  and
              newer.

       -n     Displays  the  NFS-directory  statistic.   Data  displayed  are  valid only with kernels 2.6.17 and newer.  This option is exclusive ot the -x
              option.

       -h     Display the NFS report more human readable.

       -p [ { device | ALL } ]
              The -p option is exclusive of the -x option and displays statistics for block devices and all their partitions that are used  by  the  system.
              If  a device name is entered on the command line, then statistics for it and all its partitions are displayed. Last, the ALL keyword indicates
              that statistics have to be displayed for all the block devices and partitions defined by the system, including  those  that  have  never  been
              used.  Note that this option works only with post 2.5 kernels.

       -t     Print the time for each report displayed.

       -V     Print version number then exit.

       -x     Display  extended  statistics.  This option is exclusive of the -p and -n, and works with post 2.5 kernels since it needs /proc/diskstats file
              or a mounted sysfs to get the statistics. This option may also work with older kernels (e.g. 2.4) only if extended statistics are available in
              /proc/partitions (the kernel needs to be patched for that).
 Device Utilization Report
              The  second  report  generated by the iostat command is the Device Utilization Report. The device report provides statistics on a per physical
              device or partition basis. Block devices for which statistics are to be displayed may be entered on the command line. Partitions may  also  be
              entered  on  the  command line providing that option -x is not used.  If no device nor partition is entered, then statistics are displayed for
              every device used by the system, and providing that the kernel maintains statistics for it.  If the ALL keyword is given on the command  line,
              then statistics are displayed for every device defined by the system, including those that have never been used.  The report may show the fol-
              lowing fields, depending on the flags used:

              Device:
                     This column gives the device (or partition) name, which is displayed as hdiskn with 2.2 kernels, for the nth device. It is displayed as
                     devm-n with 2.4 kernels, where m is the major number of the device, and n a distinctive number.  With newer kernels, the device name as
                     listed in the /dev directory is displayed.

              tps
                     Indicate the number of transfers per second that were issued to the device. A transfer is an I/O request to the device. Multiple  logi-
                     cal requests can be combined into a single I/O request to the device. A transfer is of indeterminate size.

              Blk_read/s
                     Indicate  the amount of data read from the device expressed in a number of blocks per second. Blocks are equivalent to sectors with 2.4
                     kernels and newer and therefore have a size of 512 bytes. With older kernels, a block is of indeterminate size.

              Blk_wrtn/s
                     Indicate the amount of data written to the device expressed in a number of blocks per second.

              Blk_read
                     The total number of blocks read.

              Blk_wrtn
 Blk_wrtn
                     The total number of blocks written.

              kB_read/s
                     Indicate the amount of data read from the device expressed in kilobytes per second.

              kB_wrtn/s
                     Indicate the amount of data written to the device expressed in kilobytes per second.

              kB_read
                     The total number of kilobytes read.

              kB_wrtn
                     The total number of kilobytes written.

              MB_read/s
                     Indicate the amount of data read from the device expressed in megabytes per second.

              MB_wrtn/s
                     Indicate the amount of data written to the device expressed in megabytes per second.

              MB_read
                     The total number of megabytes read.

              MB_wrtn
                     The total number of megabytes written.

              rrqm/s
                     The number of read requests merged per second that were queued to the device.

              wrqm/s
                     The number of write requests merged per second that were queued to the device.

              r/s
                     The number of read requests that were issued to the device per second.

              w/s
                     The number of write requests that were issued to the device per second.
              rsec/s
                     The number of sectors read from the device per second.

              wsec/s
                     The number of sectors written to the device per second.

              rkB/s
                     The number of kilobytes read from the device per second.

              wkB/s
                     The number of kilobytes written to the device per second.

              rMB/s
                     The number of megabytes read from the device per second.

              wMB/s
                     The number of megabytes written to the device per second.

              avgrq-sz
                     The average size (in sectors) of the requests that were issued to the device.

              avgqu-sz
                     The average queue length of the requests that were issued to the device.

              await
                     The average time (in milliseconds) for I/O requests issued to the device to be served. This includes the time spent by the requests  in
                     queue and the time spent servicing them.

              svctm
                     The average service time (in milliseconds) for I/O requests that were issued to the device.

              %util
                     Percentage  of  CPU  time during which I/O requests were issued to the device (bandwidth utilization for the device). Device saturation
                     occurs when this value is close to 100%.

              ops/s
                     Indicate the number of operations that were issued to the mount point per second

              rops/s
                     Indicate the number of read operations that were issued to the mount point per second

              wops/s
                     Indicate the number of write operations that were issued to the mount point per second

EXAMPLES
       iostat
              Display a single history since boot report for all CPU and Devices.

       iostat -d 2
              Display a continuous device report at two second intervals.

       iostat -d 2 6
              Display six reports at two second intervals for all devices.

       iostat -x hda hdb 2 6
              Display six reports of extended statistics at two second intervals for devices hda and hdb.

       iostat -p sda 2 6
              Display six reports at two second intervals for device sda and all its partitions (sda1, etc.)