iostat is, as the name implies, a command-line utility which displays input/output statistics for devices, partitions, RAID arrays and logical volumes.
iostat will output some not useful information once if you simply run
iostat. It takes it one run to gather actual not aggregated utilization data; it's second run will show actual information. iostat takes two numbers as arguments: A interval for displaying data and a number of data instances to output.
iostat 1 2 will output one list of disinformation and a list of actual disk utilization the next second and then it will exit.
iostat 2 10 will output i/o statistics every two seconds ten times.
Omitting a second number will make
iostat run indefinitely. It can, like most command-line programs, be terminated by pressing ctrl-c.
-h option makes
iostat show "human readable" output; that means megabytes and kilobytes is used instead of the precise amount of bytes read and written. Some prefer the
-h options, others do not.
iostat will by default output CPU utilization information followed by I/O statistics. The
-c argument will make it only display CPU information and
-d makes it only display disk (I/O) information. The default is
The iostat manual page has some more options which are not at all interesting.
iostat is a part of the sysstat package. There is no separate
iostat package available; install your distributions
sysstat package to get it. sysstat's homepage is at sebastien.godard.pagesperso-orange.fr.