Cautions and restrictions for Virtual Partition Manager

Impact on host performance

Creating and changing cache logical partitions can significantly degrade host performance and should only be performed during the initial installation and setup of the storage system or during a maintenance window. If you must perform these changes on a production machine, use Performance Monitor to verify that the write pending rate of the CLPR and CLPR0 satisfy the following formulas on all MP units:

For CLPR with decreased cache capacity

Write pending rate x cache capacity before operation / 
cache capacity after operation < 30%

The CLPR settings will be suspended if the write pending rate of any one of the MP units allocated to the operation target CLPR or CLPR0 is 50 percent or higher.

When you move resources in CLPRs, make sure that the writing pending rates of all the MP units for each CLPR are less than 50 percent at both the source and the destination. The process for changing the CLPR settings will be suspended until the write pending rates of all the MP units become less than 50 percent.

Duration of cache partition operations

Adding or changing CLPR definitions or configurations can take hours to complete.

Interoperability restrictions for cache partitioning


Application	Behaviors
ShadowImage	You cannot use ShadowImage Quick Restore functions that affect multiple CLPRs.
Volume Migration	You cannot use Volume Migration when it affects multiple CLPRs.
Universal Replicator	Universal Replicator data volumes and journal volumes can belong to different CLPRs. All journal volumes in the same journal must belong to the same CLPR. If not, an error occurs.