iostat - report I/O statistics
iostat [ option ] ... [ interval [ count ] ]
Iostat delves into the system and reports certain statistics kept about
input-output activity. Information is kept about up to three different
disks (RF, RK, RP) and about typewriters. For each disk, IO comple-
tions and number of words transferred are counted; for typewriters col-
lectively, the number of input and output characters are counted.
Also, each sixtieth of a second, the state of each disk is examined and
a tally is made if the disk is active. The tally goes into one of four
categories, depending on whether the system is executing in user mode,
in `nice' (background) user mode, in system mode, or idle. From all
these numbers and from the known transfer rates of the devices it is
possible to determine information such as the degree of IO overlap and
average seek times for each device.
The optional interval argument causes iostat to report once each inter-
val seconds. The first report is for all time since a reboot and each
subsequent report is for the last interval only.
The optional count argument restricts the number of reports.
With no option argument iostat reports for each disk the number of
transfers per minute, the milliseconds per average seek, and the mil-
liseconds per data transfer exclusive of seek time. It also gives the
percentage of time the system has spend in each of the four categories
The following options are available:
-t Report the number of characters of terminal IO per second as
-i Report the percentage of time spend in each of the four cate-
gories mentioned above, the percentage of time each disk was
active (seeking or transferring), the percentage of time any
disk was active, and the percentage of time spent in `IO wait:'
idle, but with a disk active.
-s Report the raw timing information: 32 numbers indicating the
percentage of time spent in each of the possible configurations
of 4 system states and 8 IO states (3 disks each active or not).
-b Report on the usage of IO buffers.