iostat 命令说明_man文档

XXX
XXX WARNING: old character encoding and/or character set
XXX
IOSTAT(1)                     Linux User’s Manual                    IOSTAT(1)

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

SYNOPSIS
       iostat [ -c | -d ] [ -k | -m ] [ -t ] [ -V ] [ -x ] [ -n ] [ -h ] [ device [ ... ] | ALL ] [ -p [ device | ALL ] ] [ interval [ count ] ]

DESCRIPTION
       The  iostat  command  is  used for monitoring system input/output device loading by observing the time the devices are active in relation to their average
       transfer rates. The iostat command generates reports that can be used to change system configuration to better balance the input/output load between phys-
       ical disks.

       The  first  report  generated by the iostat command provides statistics concerning the time since the system was booted. Each subsequent report covers the
       time since the previous report. All statistics are reported each time the iostat command is run. The report consists of a CPU header row followed by a row
       of CPU statistics. On multiprocessor systems, CPU statistics are calculated system-wide as averages among all processors. A device header row is displayed
       followed by a line of statistics for each device that is configured.

       The interval parameter specifies the amount of time in seconds between each report. The first report contains statistics for the time since system startup
       (boot).  Each  subsequent report contains statistics collected during the interval since the previous report. The count parameter can be specified in con-
       junction with the interval parameter. If the count parameter is specified, the value of count determines the number of reports generated at interval  sec-
       onds apart. If the interval parameter is specified without the count parameter, the iostat command generates reports continuously.

REPORTS
       The iostat command generates two types of reports, the CPU Utilization report and the Device Utilization report.

       CPU Utilization Report
              The  first  report  generated  by  the iostat command is the CPU Utilization Report. For multiprocessor systems, the CPU values are global averages
              among all processors.  The report has the following format:

              %user
                     Show the percentage of CPU utilization that occurred while executing at the user level (application).
              %nice
                     Show the percentage of CPU utilization that occurred while executing at the user level with nice priority.
              %system
                     Show the percentage of CPU utilization that occurred while executing at the system level (kernel).
              %iowait
                     Show the percentage of time that the CPU or CPUs were idle during which the system had an outstanding disk I/O request.
              %steal
                     Show the percentage of time spent in involuntary wait by the virtual CPU or CPUs while the hypervisor was servicing another virtual  proces-
                     sor.
              %idle
                     Show the percentage of time that the CPU or CPUs were idle and the system did not have an outstanding disk I/O request.

       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 following 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  logical
                     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 ker-
                     nels 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
                     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%.

              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

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).

ENVIRONMENT
       The iostat command takes into account the following environment variable:

       S_TIME_FORMAT
              If  this  variable exists and its value is ISO then the current locale will be ignored when printing the date in the report header. The iostat com-
              mand will use the ISO 8601 format (YYYY-MM-DD) instead.

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.)

BUGS
       /proc filesystem must be mounted for iostat to work.

       On SMP machines iostat assumes that CPU #0 is never disabled. Indeed iostat uses it to calculate the time interval.

       Extended statistics are available only with post 2.5 kernels.

FILES
       /proc/stat contains system statistics.

       /proc/partitions contains disk statistics (for pre 2.5 kernels that have been patched).

       /proc/diskstats contains disks statistics (for post 2.5 kernels).

       /proc/uptime contains system uptime in seconds and centiseconds (for post 2.5 kernels).

       /sys contains statistics for block devices (post 2.5 kernels).

AUTHOR
       Sebastien Godard (sysstat <at> wanadoo.fr)

SEE ALSO
       sar(1), mpstat(1), vmstat(8)

       http://perso.orange.fr/sebastien.godard/

Linux                            OCTOBER 2006                        IOSTAT(1)