Steps for evaluating how PPRC affects the primary storage subsystem

Storage subsystem use can affect overall system performance, and it is therefore necessary to determine how adding PPRC might affect the primary storage subsystem.

Perform the following steps when evaluating how PPRC affects the primary storage subsystem:

1. Determine the write rate, for each primary site storage control, for the volumes that you plan to copy.
2. Add this rate, as if it was all DASD fast write, to the total storage subsystem use.
3. Decide if this impact on the storage subsystem allows applications to achieve acceptable disk I/O performance. If it does not, you might need to redistribute volumes among storage controls or add an additional primary site storage control.

Also consider how initial volume copy and resynchronization activity affect storage control use and application performance. You might notice this when you start a copy operation, restart a system, perform some copy recovery events, or when you add volumes to the PPRC system.

If you have a storage control configured with fixed block devices and LSSs, contact your DASD vendor to understand whether your primary and secondary disk subsystem support the prerequisite level of the PPRC architecture.