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Power 6/32 Unix version 1.21

.TH IOSTAT 1 "18 January 1983"
.UC 4
.SH NAME
iostat \- report I/O statistics
.SH SYNOPSIS
.B iostat
[ [-01r] interval [ count ] ]
.SH DESCRIPTION
.I Iostat
iteratively reports the number of 
characters read and written to terminals,
and, for each disk, the number of 
seeks per second, transfers per second, 
kilobytes transferred per second,
and the milliseconds per average 
transfer which include the seek time.
It also gives the percentage of time the system has
spent in user mode, in user mode running 
low priority (niced) processes,
in system mode, and idling.
.PP
To compute this information, 
for each disk, seeks and data transfer completions
and number of words transferred are counted;
for terminals collectively, 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.
From these numbers, and given the transfer rates
of the devices, it is possible to determine
average seek times for each device.
.PP
The POWER 6/32 can support up to 32 disk drives.  
.I Iostat 
can only display 16 drives at one time.
The 
.B \-0
argument will display the first 16 mounted disk drives, 
and the
.B \-1
argument will display the second 16 mounted disk drives. 
These options take effect only if the system has more
than 16 mounted drives.
The
.B \-0
argument is the default.  
Any time during the display, you can type in
a 0, 1 or r to change the display.
.PP
The
.B \-r
argument, switches between displaying the 
first and second 16 disk drives, i.e., it switches 
back and forth between the 0 and 1 options.
This option takes effect only if the system has more
than 16 mounted drives.
The duration for each set of drives will be [interval]/2 .
.PP
The optional
.I interval
argument causes
.I iostat
to report once each
.I interval
seconds.
The first report is for  all time since a reboot and each
subsequent report is for the last interval only.
.PP
The optional
.I count
argument restricts the number of reports.
.SH FILES
/dev/kmem
.br
/vmunix
.SH SEE ALSO
vmstat(1)

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