What does iostat do?

iostat command is a command that 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 create reports that can be used to change system configuration to better balance the input/output between physical disks.

The iostat utility iteratively reports terminal, disk, and tape I/O activity, as well as CPU utilization. The first line of output is for all time since boot

 iostat  –  it shows scsi errors 
scsi errors means it shows s/w errors and h/w and tape drive errors it shows just check out

Usage: iostat [ options ] [ <interval> [ <count> ] ]
Options are:
[ -c ] [ -d ] [ -h ] [ -N ] [ -k | -m ] [ -t ] [ -V ] [ -x ] [ -z ]
[ <device> […] | ALL ] [ -p [ <device> [,…] | ALL ] ]

 

type iostat in your console

 

The first section contains CPU report

 

  • %user : show the percentage of CPU utilization that occured while executing at the user (application) level

 

The second section contains device utilization report

 

  • %nice : show the percentage of CPU utilization that occured while executing at the user level with nice priority
  • %system : show the percentage of CPU utilization that occured while executing at the system (kernel) level
  • %iowait : show the percentage of the time that the CPU or CPUs were idle during whcih 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 outstanding disk I/O request
  • Device : device / partition name as listed in /dev directory
  • tps : show the number of transfers per second that were issued to the device. Higher tps means the processor is busier
  • Blk_read/s : show the amount of data read from the device expressed in a number of blocks (kilobytes, megabytes) per second
  • Blk_wrtn/s : show the amount of data written to the device expressed in a number of blocks (kilobytes, megabytes) per second
  • Blk_read : show the total number of blocks read
  • Blk_wrtn : show the total number of blocks written

 

source: linoxide.com/linux-command/linux-iostat-command/