【Linux命令】iostat

starxzj

　　NAME
　　iostat  -  Report Central Processing Unit (CPU) statistics and input/output statistics for devices, partitions and network filesystems (NFS).
　　
　　SYNOPSIS
　　       iostat [ -c ] [ -d ] [ -N ] [ -n ] [ -h ] [ -k | -m ] [ -t ] [ -V ] [ -x ] [ -y ] [ -z ] [ -j { ID |  LABEL  |  PATH  |
　　       UUID | ... } [ device [...] | ALL ] ] [ 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 physical disks.
　　       When option -n is used, an NFS header row is displayed followed  by  a  line  of  statistics  for  each  network
　　filesystem that is mounted.
　　 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), unless the -y option is used, when this report is omitted.  Each subsequent  report  contains  statistics collected during the interval since the previous report. The count parameter can be specified in conjunction with the interval parameter. If the count parameter is specified, the value  of  count determines  the  number  of  reports generated at interval seconds apart. If the interval parameter is specified without the count parameter, the iostat command generates reports continuously.
　　REPORTS
　　       The iostat command generates three types of reports, the CPU Utilization report, the Device Utilization report and  the Network Filesystem 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 processor.
　　   %idle
　　             Show  the  percentage  of  time that the CPU or CPUs were idle and the system did not have an outstandin  disk I/O request.
　　   Device Utilization Report(列出一部分)
　　        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.
　　        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.
　　        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.
　　
　　        %util
　　             Percentage of elapsed 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%.
　　OPTIONS
　　       -c     Display the CPU utilization report.
　　

　　       -d     Display 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 later.
　　       -x     Display  extended  statistics.  This option 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).