7.1.2. The iostat command.

The iostat will display the current CPU load average and disk I/O information. This is a great command to monitor your disk I/O usage.

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# **iostat**
Linux 2.4.20-24.9 (myhost)       12/23/2003

avg-cpu:  %user   %nice    %sys   %idle
          62.09    0.32    2.97   34.62

Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
dev3-0            2.22        15.20        47.16    1546846    4799520

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For 2.4 kernels the devices is names using the device's major and minor number. In this case the device listed is /dev/hda. To have iostat print this out for you, use the -x.

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# **iostat -x**
Linux 2.4.20-24.9 (myhost)       12/23/2003

avg-cpu:  %user   %nice    %sys   %idle
          62.01    0.32    2.97   34.71

Device:  rrqm/s wrqm/s r/s  w/s rsec/s wsec/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util
/dev/hdc   0.00   0.00 .00 0.00   0.00   0.00  0.00  0.00     0.00     2.35  0.00  0.00 14.71
/dev/hda   1.13   4.50 .81 1.39  15.18  47.14  7.59 23.57    28.24     1.99 63.76 70.48 15.56
/dev/hda1  1.08   3.98 .73 1.27  14.49  42.05  7.25 21.02    28.22     0.44 21.82  4.97  1.00
/dev/hda2  0.00   0.51 .07 0.12   0.55   5.07  0.27  2.54    30.35     0.97 52.67 61.73  2.99
/dev/hda3  0.05   0.01 .02 0.00   0.14   0.02  0.07  0.01     8.51     0.00 12.55  2.95  0.01

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The iostat man page contains a detailed explanation of what each of these columns mean.