FAST Cache is a large capacity secondary cache that uses SAS Flash 2 drives to improve system performance. FAST Cache uses the Flash disks for the most frequently accessed data in the storage system instead of dedicating Flash disks to a particular application. Individual storage pools can be configured to use the FAST Cache, so that all storage resources created in those pools use the FAST Cache.
How to enable FAST Cache via Unisphere GUI, Settings > Storage Configuration > FAST Cache > Create. Select the FAST Cache disks from available SAS Flash drives and choose whether to enable FAST Cache for existing pools.