You can change the MP unit (MP blade) assignment settings for resources (logical devices, external volumes, or journals) only by using CCI.
When changing the MP unit assigned to an LDEV, MP units of multiple LDEVs might be changed at the same time depending on utilization of software (Thin Image, ShadowImage, Volume Migration, or Universal Replicator). If the MP unit ID is changed under high load, I/O delays might occur and impact the operations. Verify the following restrictions before changing the MP unit ID.
- Change the MP unit ID of an LDEV during off-peak hours when the I/O load is as low as possible. Do not change the MP unit ID when the I/O load is high, for example, during initial copy of ShadowImage, TrueCopy, global-active device, or Universal Replicator.
- After you change the MP unit ID of an LDEV, wait more than 30 minutes before you try to change the MP unit ID of the same LDEV again.
- When you change the MP unit ID of an LDEV, use Export Tool 2. Calculate the performance information based on the outputs of Export Tool 2 before and after the change, and then verify the load status of the system.
- Change the MP unit ID of an LDEV when the cache write-pending rate (%) of the MP unit is lower than 50% before and after the changes.
- Do not change MP unit IDs of many LDEVs at one time. As a guideline, set the number of LDEVs whose MP unit IDs are changed at one time and the load placed on the changed LDEVs to 10% or less of all LDEVs with the same MP unit ID assigned.