Use the Character-Cell Real-time Display › Evaluate Performance Using the Investigate Displays › Investigate an I/O Limitation

Investigate an I/O Limitation

The chief indicators of an I/O limitation are as follows:

Direct I/O high

Look at the value of Dir I/O, as well as Data in the disk bar histogram.

Dir I/O gives the system-wide direct I/O rate, including all disks. If there is a high direct I/O rate for your system, the disks might be a bottleneck. A value for direct I/O rate that exceeds this number indicates a high direct I/O rate.

Data in the disk bars shows how much of the disk's time is spent doing I/O on behalf of the user. A high rate for a given disk may indicate that the disk is a bottleneck.

Buffered I/O high

A high value of Buf I/O (the buffered I/O rate) may indicate an I/O limitation. If the value of Buf I/O exceeds this number, a high buffered I/O rate is indicated.