When the data on the and the that are participating in a are no longer synchronized, the of the primary logical drive performs a copy operation to the data between the mirrored pair.
The current owner of the primary logical drive performs this operation in the background. At the same time, the controller processes local I/O writes to the primary logical drive and associated to the secondary logical drive. Because the resynchronization diverts controller processing resources from I/O activity, resynchronization can have a performance impact to the application. The defines how much processing time is allocated for synchronization activities relative to system performance.
Keep these guidelines in mind to help you determine how long a synchronization priority might take and how much various synchronization priorities can affect system performance.
These priority rates are available:
The lowest priority rate supports system performance, but the resynchronization takes longer. The highest priority rate supports the resynchronization, but system performance might be compromised. These guidelines roughly approximate the differences between the five priorities. size and host I/O rate loads affect the synchronization time comparisons.
Priority Rate for Full Synchronization | Time Elapsed Compared to Highest Synchronization Rate |
---|---|
Lowest | Approximately eight times as long as at the highest priority rate. |
Low | Approximately six times as long as at the highest priority rate. |
Medium | Approximately three-and-a-half times as long as at the highest priority rate. |
High | Approximately twice as long as at the highest priority rate. |