With this config (assuming a "load balance" HA Setup) you are not facing the raidgroup size question...
two controllers / each with one aggr0 of 11 disks, leaving 1 spare disk per controller...
Peter
PS default raidgroup size with SAS disks is 16 disks per RG (max 28)
RAID-DP (Default)
ATA/BSAS/SATA: 14 FC/SAS: 16 SSD: 23
(Maximum)
ATA/BSAS/SATA: 20 FC/SAS: 28 SSD: 28
RAID4 (default)
ATA/BSAS/SATA: 7 FC/SAS/SSD: 8
(Maximum)
ATA/BSAS/SATA: 7 FC/SAS/SSD: 14