The in-depth perspective of this white paper should have provided the reader with sufficient understanding and the required knowledge to describe the components and technologies involved with Symmetrix Optimizer. The setup and configurations screens are particularly useful to help guide the reader through the various configuration scenarios and the required customization based on user needs.
Finally, and most important, the reader should also appreciate how Symmetrix Optimizer provides significant benefit to customers’ enterprises by enhancing the predictability of mission-critical information performance.
Appendix A: Symmetrix Optimizer and TimeFinder in Enginuity versions prior to 5568
Optimizer and TimeFinder both use the Symmetrix feature of dynamic mirroring. With this feature, a special volume like the BCV or DRV can become a mirror copy of a Symmetrix volume. In Enginuity revisions before 5x68xxxxx, there are potential interactions between BCVs and DRVs due to the rules of dynamic mirroring. With careful setup, TimeFinder and Optimizer can be used successfully with these code revisions. If the customer’s TimeFinder environment is complex, it is best to upgrade to release 5x68xx of the Enginuity microcode.
Unlike the DRV, a BCV has additional attributes that allow it to independently support host applications and processes. It may be configured as a single mirror, a locally mirrored device, or an SRDF® source (R1) device. A BCV device can be RAID 1 or RDF protected, but it cannot be RAID-S protected.
The Optimizer’s DRV differs from a TimeFinder BCV in that it cannot be connected to a host, and it has no need for mirror protection.
Scenario 1: TimeFinder’s BCV is synchronized with a volume that Optimizer wants to swap.
If a BCV is already established to the volume selected by Optimizer to be swapped, Optimizer will reject that swap pick and make the next best swap pairing. Optimizer will check for a significant performance improvement before doing a swap. The final swap pick will be sent to SymmWin for swapping. This behavior benefits the performance of the Symmetrix system, and does not present a problem.
But, if the volume that comes up at the top of the swap list is always paired with a BCV during the Optimizer swap window, Optimizer will not be able to correct the performance issue. The Optimizer swap window should not align exactly with the window for establishing BCVs.
Remember that a user may leave the BCV established to the STD volume for a long period of time. If this is the case, there is a high probability the Optimizer’s swap selection will be affected by this interaction scenario. The interaction can be eliminated by implementing one of the two solutions listed in the next section, “Solution sets.”
Scenario 2: Optimizer is swapping a volume TimeFinder wants.
If Optimizer is swapping a volume that TimeFinder attempts to establish a BCV with, the TimeFinder action will fail and give a return code error. The script needs to check the return code and one of the following solutions is needed to correct the error.
The time of the Optimizer swap is approximately twice the length of time is takes to establish a BCV to a standard. This is a relatively short period. The probability of this interaction scenario is small. But the consequence to TimeFinder can be great, and every effort should be made to avoid this interaction. Again, the interaction can be eliminated by implementing one of the two solutions listed in the next section.
EMC Symmetrix Optimizer A Detailed Review