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FAST Cache is a single global resource that can improve performance of one or more hybrid pools within a Dell Unity hybrid system. FAST Cache can only be created with SAS Flash 2 drivesI, and is only applicable to hybrid pools. It is recommended to place a Flash tier in the hybrid pool before configuring FAST Cache on the pool. FAST Cache can improve access to data that is resident in the HDD tiers of the pool.
Enable FAST Cache on the hybrid pool if the workload in that pool is highly transactional, and has a high degree of locality that changes rapidly.
For applications that use larger I/O sizes, have lower skew, or do not change locality as quickly, it may be more beneficial to increase the size of the Flash tier rather than enable FAST Cache.
FAST Cache can increase the IOPS achievable from the Dell Unity system, and this will most likely result in higher CPU utilization (in order to service the additional I/O). Before enabling FAST Cache on additional pools or expanding the size of an existing FAST Cache, monitor the average system CPU utilization to determine if the system can accommodate the additional load. Refer to Table 2 for recommendations.