Priority control is a suitable solution for setting relative priority levels for individual services. On the other hand, priority control for QoS groups is a suitable solution for setting relative priority levels for a tenant that handles multiple services. Use priority control depending on the use case.
Priority settings
There are three priority levels. The I/O processing for volumes or QoS groups with higher priority takes priority, and the I/O processing for volumes or QoS groups with lower priority is delayed. If the setting is not balanced (for example, only the high-level priority is specified), the arrangement of the processing order is not performed. If you set priorities for individual volumes, specify the high priority level for about 10%, the medium priority level for about 30%, and the low priority level for about 60% of the total number of volumes. If you set priority levels for QoS groups, specify the high priority level for about 10%, the medium priority level for about 30%, and the low priority level for about 60% of the total number of QoS groups. If individual services have almost the same priority level, priority control is not a suitable solution.
When a response delay alert is issued
Consider the following causes when a response delay alert is issued or the monitor information is abnormal during operations:
- A hardware failure (such as a drive failure) might occur. (In this case, a SIM indicating hardware failure is reported.)
- The number (or amount) of issued I/O requests might exceed the processing capacity of the storage system.
In other causes, the priority control might not be satisfactory. Consider releasing the priority setting.