We recently purchased a FAS 2240-2 and FAS 2240-4 to replace our existing SAN, but I've got some time to play around and get familiar with them. Anyway, the SE that configured the systems for us really led us astray, and specified four 200GB SSDs in each unit to give us 400 GB of Flash Pool on only one of the heads in each FAS. We were told 400 GB is the current pool size limit.
What we didn't realize is that in the hybrid aggr, the SSD raid group must match the RAID protection of the HDD group, and since we went with RAID-DP, the SSD group must be RAID-DP. So one data, one parity, one d-parity, and one hot spare. This leaves us with only 200GB flash pool, and three SSDs just for RAID, ridiculous! I didn't know this until the installers came out and set everything up, and I'm still steaming from it. I tried to convince the installer that couldn't be the case, but he called several guys he works with and they said the console wouldn't let you do it if you tried, it must be RAID-DP, and it must have a hot spare.
But looking through some docs today, I saw that it may be possible to convert the SSD RAID group to RAID4:
Another option is to add the hot spare into the RAID group I think. But I'm afraid the system will complain about not having a hot spare. With RAID4, we'd have two data, one parity, and a hot spare, giving us the maximum 400GB flash pool size.
Any thoughts? Should I just leave it alone and deal with only having 200GB flash pool?