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1 | .\" Copyright (c) 1985 The Regents of the University of California. |
2 | .\" All rights reserved. | |
3a672b8e | 3 | .\" |
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4 | .\" %sccs.include.proprietary.roff% |
5 | .\" | |
6 | .\" @(#)iostat.8 6.3 (Berkeley) %G% | |
3a672b8e | 7 | .\" |
e9463a60 | 8 | .TH IOSTAT 8 "" |
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9 | .UC 4 |
10 | .SH NAME | |
11 | iostat \- report I/O statistics | |
12 | .SH SYNOPSIS | |
13 | .B iostat | |
d8f06b41 | 14 | [ drives ] |
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15 | [ interval [ count ] ] |
16 | .SH DESCRIPTION | |
17 | .I Iostat | |
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18 | iteratively reports the number of characters read and written to terminals |
19 | per second, | |
20 | and, for each disk, the number of transfers per second, kilobytes | |
21 | transferred per second, | |
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22 | and the milliseconds per average seek. |
23 | It also gives the percentage of time the system has | |
24 | spent in user mode, in user mode running low priority (niced) processes, | |
25 | in system mode, and idling. | |
26 | .PP | |
27 | To compute this information, for each disk, seeks and data transfer completions | |
28 | and number of words transferred are counted; | |
29 | for terminals collectively, the number | |
30 | of input and output characters are counted. | |
31 | Also, each sixtieth of a second, | |
32 | the state of each disk is examined | |
33 | and a tally is made if the disk is active. | |
34 | From these numbers and given the transfer rates | |
35 | of the devices it is possible to determine | |
36 | average seek times for each device. | |
37 | .PP | |
38 | The optional | |
39 | .I interval | |
40 | argument causes | |
41 | .I iostat | |
42 | to report once each | |
43 | .I interval | |
44 | seconds. | |
45 | The first report is for all time since a reboot and each | |
46 | subsequent report is for the last interval only. | |
47 | .PP | |
48 | The optional | |
49 | .I count | |
50 | argument restricts the number of reports. | |
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51 | .PP |
52 | If more than 4 disk drives are configured in the system, | |
53 | .I iostat | |
54 | displays only the first 4 drives, with priority given | |
55 | to Massbus disk drives (i.e. if both Unibus and Massbus | |
56 | drives are present and the total number of drives exceeds | |
57 | 4, then some number of Unibus drives will not be displayed | |
58 | in favor of the Massbus drives). To force | |
59 | .I iostat | |
60 | to display specific drives, their names may be supplied on | |
61 | the command line. | |
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62 | .SH FILES |
63 | /dev/kmem | |
df667069 | 64 | .br |
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65 | /vmunix |
66 | .SH SEE ALSO | |
67 | vmstat(1) |