CPU utilization

The CPU utilization graph shows the current percentage of CPU usage and peaks in utilization. It can also display compression CPU usage for systems with compressed volumes.

If you have a IBM® Real-time Compression™ license, you can also monitor the system resources by selecting System % and Compression %. If compression is active, the system partitions the CPU resources on all nodes with compressed volumes, reserving a portion for compression functions and a portion for the remaining system functions. The utilization data is scaled to 100%. If either partition reaches capacity, the system or node as a whole is limited. For example, if 10% compressed CPU utilization is displayed, it is actually 10% of the compression partition. If 20% of the non-compressed CPU utilization is displayed, it is 20% of the system partition that is used.

The gradient at the top of the graph indicates when any data point is above 95% system CPU utilization. A single spike often does not indicate a performance impact on the system; however, if a data point for the system is consistently above 95% of utilization and I/O input is high, the system might be overloaded, which might indicate a need for more back-end storage. However, for compression utilization alone, it can be normal to see rates at 100%, especially if compression is used frequently on the system. If both compression and I/O input is high, the system might need additional storage to accommodate the utilization.

When you use compression, monitor overall performance and CPU utilization to ensure that other system functions have adequate bandwidth. If compression is used excessively, overall bandwidth for the system might be impacted.