If I wanted to make a nice drive array I'd look at the DROBO 4 bay unit then slip in 4 of the new 2.5 inch hybrid drives. With all the extra air space the drives will be nice and cool (heat kills) and the DROBO's RAID features let us replace drives as they fail. I doubt such will fail for years.

Then again most folk with the above story just get the biggest 4TB external drives they can and then place them on some baking rack with a fan to cool the lot. That's pretty cheap!
Bob