I have a FreeNAS system running on a semi-old Supermicro server. It has a variant of this backplane, but with only one daughter card (so 3 SAS connections).
I currently have an 1-port LSI HBA which connects to the backplane. I’ve replaced it with a new 2-port HBA which is great, but I’m left with a spare 1-port HBA and 1 empty SAS port on the backplane.
My question is, what caveats, if any, come with plugging 2 SAS ports into one HBA and 1 into another? Is FreeBSD smart enough to load-balance all 3? Will it choose one HBA and fail over to the other? If so, how does it choose?
This is uncharted territory for me. Currently I just have the new HBA connected to 2 ports and the old HBA installed but not plugged into anything.
So, now you have an 8 lane connection to the expander. This effectively doubles the bandwidth available between the expander and that hba. Connecting the other remaining hba port to the expander will make the drives also visible on the that hba. If freenas has some sort of multi-path io software it will determine that there are multiple paths to the same drives. Load balancing, maybe, maybe not. If one hba failed freenas could get to the drives thru the other hba. Does all that kind of stuff work on freenas, idk.