Disk Load Monitoring

If a system is under a heavy I/O load, then the load should be spread across as many disks and disk controllers as possible. To see what the load looks like, use the iostat command or one of the SE toolkit variants.

Output Formats and Options for iostat

The iostat command produces output in many forms. The iostat -x variant provides extended statistics and is easier to read when a large number of disks are being reported, since each disk is summarized on a separate line (see Figure 8-2). The values reported are the number of transfers and kilobytes per second, with read and write shown separately; the average number of commands waiting in the queue; the average number of commands actively being processed by the drive; the I/O service time; and the percentages of the time that commands were waiting in the queue; and commands that were active on the drive.