Hi
If you want to make most of the space
You should be seperate 12 disk
you should be assign 10 disk controller A
you sohuld be assign 2 controller B
ControllerA
you can create aggr0 with 9 disk ---1 disk is spare--total 10
aggr0 with 9 disk-------7 data----2 parity--RaidDP
Controller B
you can create aggr0 with 2 disk
aggr0-1 data-1 parity disk-- no spares Raid4---But not recomended (on root volume )
if you want right config
Assign 8 disk to controller A and create raiddp aggr with 7 disk and its also inculede ( 5data-2 parity ) and 1 spare total 8 disk
assign 4 disk controller B create raiddp aggr
aggr0- 3 disk (1data-2 parity)- 1 spare