The FAS2240-2 is a 2u SAS shelf and does not allow for anything but SAS drives internal, but the FAS2240-4 is a 4u SAS shelf and does allow this. From the FlashPool FAQ below... The part numbers for the 2240-4 allow for all SSD internally (24x 100GB) or a mix of 6x 100GB and 18x1 or 3TB drives. For 2TB it is supported but is not a part number so the drives are ordered individually.
FAS2240-4 and FAS2220 internal drive options:
o F2240A-4-12X100-SSD-R5, FAS2240-4,HA,12X100GB,SSD,Dual CTL
o F2240A-4-18TB-24M-R5, FAS2240-4,6x100GB,18x1TB,Mixed,Dual CTL
o F2240A-4-24X100-SSD-R5, FAS2240-4,HA,24X100GB,SSD,Dual CTL
o F2240A-4-54TB-24M-R5, FAS2240-4,6x100GB,18x3TB,Mixed,Dual CTL
o FAS2220A-12X100-SSD-R6, FAS2220,HA,12x100GB,SSD,Dual CNTLR