The Flash Pool technology enables you to add one or more RAID groups composed of SSDs to an aggregate that consists of HDD RAID groups.
The SSD cache does not contribute to the size of the aggregate as calculated against the maximum aggregate size. For example, even if an aggregate is at the maximum aggregate size, you can add an SSD RAID group to it. The SSDs do count toward the overall (node or HA pair) drive limit.
The HDD RAID groups in a Flash Pool aggregate behave the same as HDD RAID groups in a standard aggregate, following the same rules for mixing disk types, sizes, speeds, and checksums. For example, you cannot combine performance and capacity disks in the HDD RAID groups of a Flash Pool aggregate.
The checksum type, RAID type, and RAID group size values can be configured for the SSD cache RAID groups and HDD RAID groups independently.
There is a platform-dependent maximum size for the SSD cache. For information about this limit for your platform, see the Hardware Universe.