1IOSTAT(1) General Commands Manual IOSTAT(1)
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6 iostat - report I/O statistics
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9 iostat [ drives ] [ interval [ count ] ]
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12 Iostat iteratively reports the number of characters read and written to
13 terminals per second, and, for each disk, the number of transfers per
14 second, kilobytes transferred per second, and the milliseconds per
15 average seek. It also gives the percentage of time the system has
16 spent in user mode, in user mode running low priority (niced) pro‐
17 cesses, in system mode, and idling.
18 To compute this information, for each disk, seeks and data transfer
20 completions and number of words transferred are counted; for terminals
21 collectively, the number of input and output characters are counted.
22 Also, each sixtieth of a second, the state of each disk is examined and
23 a tally is made if the disk is active. From these numbers and given
24 the transfer rates of the devices it is possible to determine average
25 seek times for each device.
26 The optional interval argument causes iostat to report once each inter‐
28 val seconds. The first report is for all time since a reboot and each
29 subsequent report is for the last interval only.
30 The optional count argument restricts the number of reports.
32 If more than 4 disk drives are configured in the system, iostat dis‐
34 plays only the first 4 drives, with priority given to Massbus disk
35 drives (i.e. if both Unibus and Massbus drives are present and the
36 total number of drives exceeds 4, then some number of Unibus drives
37 will not be displayed in favor of the Massbus drives). To force iostat
38 to display specific drives, their names may be supplied on the command
39 line.
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42 /dev/kmem
43 /vmunix
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46 vmstat(1)
474th Berkeley Distribution April 29, 1985 IOSTAT(1)