projects / unix-history / blame
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|---|---|---|
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1 | .\" Copyright (c) 1980 Regents of the University of California. |
| 2 | .\" All rights reserved. The Berkeley software License Agreement | |
| 3 | .\" specifies the terms and conditions for redistribution. | |
| 4 | .\" | |
| d8f06b41 | 5 | .\" @(#)iostat.8 6.1 (Berkeley) %G% |
| 3a672b8e | 6 | .\" |
| d8f06b41 | 7 | .TH IOSTAT 1 "" |
| 3a672b8e KM |
8 | .UC 4 |
| 9 | .SH NAME | |
| 10 | iostat \- report I/O statistics | |
| 11 | .SH SYNOPSIS | |
| 12 | .B iostat | |
| d8f06b41 | 13 | [ drives ] |
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14 | [ interval [ count ] ] |
| 15 | .SH DESCRIPTION | |
| 16 | .I Iostat | |
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17 | iteratively reports the number of characters read and written to terminals |
| 18 | per second, | |
| 19 | and, for each disk, the number of transfers per second, kilobytes | |
| 20 | transferred per second, | |
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21 | and the milliseconds per average seek. |
| 22 | It also gives the percentage of time the system has | |
| 23 | spent in user mode, in user mode running low priority (niced) processes, | |
| 24 | in system mode, and idling. | |
| 25 | .PP | |
| 26 | To compute this information, for each disk, seeks and data transfer completions | |
| 27 | and number of words transferred are counted; | |
| 28 | for terminals collectively, the number | |
| 29 | of input and output characters are counted. | |
| 30 | Also, each sixtieth of a second, | |
| 31 | the state of each disk is examined | |
| 32 | and a tally is made if the disk is active. | |
| 33 | From these numbers and given the transfer rates | |
| 34 | of the devices it is possible to determine | |
| 35 | average seek times for each device. | |
| 36 | .PP | |
| 37 | The optional | |
| 38 | .I interval | |
| 39 | argument causes | |
| 40 | .I iostat | |
| 41 | to report once each | |
| 42 | .I interval | |
| 43 | seconds. | |
| 44 | The first report is for all time since a reboot and each | |
| 45 | subsequent report is for the last interval only. | |
| 46 | .PP | |
| 47 | The optional | |
| 48 | .I count | |
| 49 | argument restricts the number of reports. | |
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50 | .PP |
| 51 | If more than 4 disk drives are configured in the system, | |
| 52 | .I iostat | |
| 53 | displays only the first 4 drives, with priority given | |
| 54 | to Massbus disk drives (i.e. if both Unibus and Massbus | |
| 55 | drives are present and the total number of drives exceeds | |
| 56 | 4, then some number of Unibus drives will not be displayed | |
| 57 | in favor of the Massbus drives). To force | |
| 58 | .I iostat | |
| 59 | to display specific drives, their names may be supplied on | |
| 60 | the command line. | |
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61 | .SH FILES |
| 62 | /dev/kmem | |
| df667069 | 63 | .br |
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64 | /vmunix |
| 65 | .SH SEE ALSO | |
| 66 | vmstat(1) |