RAID subsystems and rank contention

RAID subsystems consist of one or more physical volumes with a possible volume for parity. The subsystem is referred to as a rank or array.

Data can be striped across a physical rank to create multiple logical volumes or multiple logical devices that can use the same physical device. The number of internal device paths to each rank or array can vary. However, only one actuator exists per physical device. If more than one volume per rank or array is being read or written to during a TDMF migration, the performance of that volume migration can be adversely impacted.

Ensure that a RAID subsystem read and write session involves only one volume per rank. Otherwise, severe performance problems can result.

Review the mapping of logical to physical volumes on a RAID subsystem to avoid overloading a physical volume within the array or rank.