I'd like to check if I put in a X9DR7-TF+ into a 846A or 846BA, do I still have space to mount 2 x 2.5” HDD into the chassis (846A), or is it better to use 846BA as it already has the built-in 2 x 2.5” HDD slot?
Both 846A and 846BA have internal 2.5 HDD support option. The main difference is 846B can have “Hot swap” 2X2.5 HDD option which can give customer flexibility to maintain their system. 846BA supports 2x 2.5 hot-swap HDD at rear panel. Please note the rear HDD is an optional feature. It does not come with the chassis by standard. The optional rear HDD kit is sold separately.