V7M/man/man1/iostat.1m

.TH IOSTAT 1M 
.SH NAME
iostat \- report I/O statistics
.SH SYNOPSIS
.B iostat
[ option ] ...
[ drive ] ...
[ interval [ count ] ]
.SH DESCRIPTION
.I Iostat
delves into the system and reports certain statistics kept about
input-output activity.
Information is kept about up to six different disks
(HP, HM, HK, ML, RP, RL) and about typewriters.
For each disk drive, I/O completions and number of words transferred
are counted; for typewriters collectively, the number
of input and output characters are counted.
Also, each sixtieth of a second,
the state of each disk drive is examined
and a tally is made if the disk drive is active.
The processor state is also examined,
this 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.
The
.I iostat
reports are for all types of activity,
seeks as well as data transfers,
on all drives that have had any I/O
activity since the system was booted,
inactive and nonexistent drives are ignored.
.PP
The optional
.I drive
argument allows the reports to be limited to
a specified subset of the available drives.
Up to six drive names, of the form;
hp0, ml1, rl3, rp4, etc., may be specified.
Reports will be generated for only those
drives which exist and have been active.
.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.
.PP
With no option argument
.I iostat
reports for each disk the number of transfers per minute,
the milliseconds
per average seek,
and the milliseconds per data transfer exclusive of seek time.
It also gives the percentage of time the system has
spend in each of the four categories mentioned above.
.PP
The following options are available:
.TP
.B \-t
Report the number of characters of terminal IO per second as well.
.TP
.B \-i
Report the percentage of time spend in each
of the four categories mentioned above,
the percentage of time each disk controller was active
(seeking or transferring,
the percentage of time any diks drive was active,
and the percentage of time spent in `IO wait:'
idle, but with a disk drive active.
.TP
.B \-s
Report the raw timing information for each
active disk drive.
The information consists of;
the disk controller name and drive number,
the disk's transfer rate (microseconds/word),
the percentage of the total system time that the
drive had I/O activity,
the number of transfers on that drive,
and the number of words transferred by the drive.
.TP
.B \-b
Report on the usage of I/O buffers.
The report gives;
the number of buffers in the pool,
the number of buffered reads,
number of read-ahead blocks, number of buffer cache hits,
number of buffered writes, and
the number of I/O operations on each buffer
starting with the first one.
.TP
.B \-d
Print the date and time at the head of the report.
.TP
.B \-a
Print the total time in minutes at the end of the report.
.SH FILES
/dev/mem, /unix
.SH BUGS
The accuracy of the 
.I iostat
reports is subject to the sixtieth
of a second granularity of the system clock.