First like drives are grouped together.  3 x EFD 10 x FC 9 x SATA  I'm making the following assumptions to keep this simple: 1) SATA are not the new EFD-SATA drives. 2) All of the FC drives are the same capacity  First the storage system will attempt to make as many (4+1) R-5 groups as possible in the individual disk group types. The remaining drives, as long as they meet or exceed the minimum required drives for R-5 (which is 3 drives) will be configured into another RG.  If there were not enough drives remaining to build another RG then they would be distributed across the other RGs of that drive type.  For example, if you had 8 x SATA you would get a (7+1) R-5 RG.  If you had 12 x SATA you would get two (5+1) R-5 RGs.  If you had 17 x SATA you would get two (5+1) R-5 RGs and one (4+1) R-5 RG.  Hope that makes sense. It gets a little trickier if you mix like drive types of different capacities.   Your configuration will look like:  1 x EFD (2+1) R-5 RG 2 x FC (4+1) R-5 RGs 1 x SATA (4+1) R-5 RG 1 x SATA (3+1) R-5 RG
I've looked around and can't find the answer to this in any white paper so hope someone here knows the answer.  I have seen that best practice is to add drives in multiples of 5 for Raid 5, 8 for Raid 6 and 1/0.  When I create a pool with a mixture of drives as follows to use for FAST how does it determine the underlying RAID layout. The number of drives is fixed due to the number of DAEs and space available.  I want a RAID 5 pool.  I want the mininimum EFD drives which I i know is 2+1?  I want 10 FC drives - would this create 2 x 4+1 Raid Groups or a 9+1?  I want 9 SATA drives - how would this be configured?  Also as a side question when adding disk to a Raid 1/0 pool do you still add each mirrored pair from two different DAEs one pair at a time?  Any answer welcome.  Thanks.
CLARiiON Storage Pools and underlying RAID layout in Flare 30