You create a Flash Pool aggregate by enabling the feature on an existing aggregate composed of HDD RAID groups, and then adding one or more SSD RAID groups to that aggregate. This results in two sets of RAID groups for that aggregate: SSD RAID groups (the SSD cache) and HDD RAID groups.
Using fewer RAID groups in the SSD cache reduces the number of parity disks required, but larger RAID groups require RAID-DP.
After you add an SSD cache to an aggregate to create a Flash Pool aggregate, you cannot remove the SSD cache to convert the aggregate back to its original configuration.
By default, the RAID level of the SSD cache is the same as the RAID level of the HDD RAID groups. You can override this default selection by specifying the raidtype option when you add the first SSD RAID groups.
If the HDDs and the SSDs do not have the same checksum type, or if the aggregate is a mixed-checksum aggregate, then you must use the checksumstyle parameter to specify the checksum type of the disks you are adding to the aggregate.
You can specify a different RAID type for the SSD cache by using the raidtype parameter.
If you want the cache RAID group size to be different from the default for the RAID type you are using, you should change it now, by using the -cache-raid-group-size parameter.