Symmetrix Optimizer can optimize all open system and mainframe RAID 1 (mirrored), RAID 5 (3+1 and 7+1), RAID 6 (6+2 and 14+2), and RDF-protected volumes in an array. Optimizer does not work with volumes configured for use with the AS/400 operating system. Optimizer does not consider business continuance volumes (BCVs), dynamic reallocation volumes (DRVs), SFS devices, target of SNAP devices, thin devices, and thin data pools for swapping (refer to the “Legality of swaps” section on page 12 for a more complete list).
In order for Symmetrix Optimizer to function, DRVs must first be configured and Symmetrix Optimizer enabled by EMC from the service processor. It is important to understand Optimizer’s requirement of an open mirror position.
Dynamic Reallocation Volumes (DRV technology)
The DRV is a non-user-addressable logical volume used by Symmetrix Optimizer to temporarily hold customer data while reconfiguration (on logical volume granularity) is executed. Data is available and protected during the reconfiguration process.
As a minimum, two DRVs must be configured for each size and emulation of volume to be swapped by Optimizer. For example, for Optimizer to swap 4 GB open-system volumes, then two 4 GB open system DRVs must be configured. If more than one simultaneous swap is desired, then additional DRVs are needed (two for each swap). If there are volumes of mixed size or emulation within the same Symmetrix frame, then DRVs are required for each size and type to be swapped.
RAID 6 devices or devices with at least three local copies of data do not require DRVs for swapping.
Interaction with TimeFinder
With the introduction of the features for concurrent BCVs and independent splits in Enginuity 5568.49.18, the direct conflicts between TimeFinder and Optimizer have been eliminated. In earlier versions of Enginuity, there was a potential for either Optimizer or TimeFinder to fail in its intended task if both attempted to operate on the same volume at the same time. For specifics on this interaction in Enginuity 66 and 67 and how to avoid the potential conflict, refer to “Appendix A: Symmetrix Optimizer and TimeFinder in Enginuity versions prior to 5568” on page 32.
Requirement for open mirror position
Optimizer does have a requirement for an open mirror position to be able to perform a swap. This limitation is the four mirror slots for a volume on the Symmetrix system. So, for example, if a RAID 1 device already has two BCVs established (that is, mmBB), then if Optimizer wants to swap this device it cannot get a mirror slot for the DRV. If Optimizer does not have a mirror slot available, then it will drop the swap and rerun the analysis. If Optimizer is in Rollback, Manual, or User-Approved mode, then Optimizer will retry a number of times and eventually stop an error if a mirror slot does not become available.
Requirement for open configuration lock
In order for Optimizer to perform a swap or a migration, it needs to hold the configuration lock. The configuration lock is an exclusive lock on the Symmetrix system for performing configuration changes. This lock prevents multiple applications from changing the Symmetrix configuration at the same time. If another application (such as SDR) holds the configuration lock when Optimizer wants to create a swap, then Optimizer will behave as previously stated (no open mirror position). Optimizer will hold the configuration lock for the duration of the swap, so other applications will not have the ability to perform configuration changes during this time.
EMC Symmetrix Optimizer A Detailed Review