In an xSP environment, the service provider can divide the Symmetrix disks into pools, and then assign each pool to a different customer. The service provider can then differentiate higher levels of service by assigning higher priority to specific pools.
In a corporate or multi-division environment, the storage manager can divide and provide different levels of service to different departments.
Disk exclude A user may choose to exclude groups of disks from the optimization process.
Example/use case: In an xSP environment, the system administrator is satisfied with the performance of a group of disks and wants to maintain the same configuration for this group.
In tier storage the system administrator does not want to spend Optimizer cycles on capacity and low priority storage.
Intra disk This feature specifies that only intra-disk moves are allowed for a group of disks provided by the user. Even though the benefits of load balancing cannot be achieved on these disks, there can still be improvement in performance obtained by reducing seek time and transfer time. This rule is useful in extreme cases where inter-disk moves are limited.
Example/use case: For Symmetrix systems where striping is heavily used, any inter-disk move may result in two or more devices from the same stripe group residing on the same disk and reducing performance. By performing only intra-disk moves on the disks with striped volumes, this can be avoided .
Volume avoidance ― Given a device group for volume avoidance, the Symmetrix Optimizer will not suggest moves that will place two or more volumes in the device group on the same disk.
A DB administrator may have some information stored in several volumes. Even though this information is not accessed most of the time, when it is needed, it is important that the information is accessed quickly. These volumes should not be situated on the same disk by any move. This can be achieved by creating them as a list for avoidance.
Idle metavolumes. Placing any of two metavolume members on the same disk may degrade performance. If the meta is active, Optimizer probably would not put any two members on one disk, but in many cases metavolumes are defined and not used for a while. During these idle times, Optimizer may swap these volumes and may locate them on the same disk, so device avoidance can be used in order to avoid such a scenario.
Do not divide the Symmetrix disks into too many pools. Too many restrictions may paralyze the Optimizer from finding the optimum back-end layout.
Use device avoidance whenever you define new metavolumes or highly correlated volumes that will only be used later. Idle volumes may be used as target volumes for swaps and become bottlenecks when they are finally used.
EMC Symmetrix Optimizer A Detailed Review