Ever since I bought into Unraid and started adding hard drives I've been thinking about what the perfect case would be. I'm using the NORCO RPC-450 4U Rackmount Server Case
which has the benefit of being pretty inexpensive but only holding 10 drives without adding some drive cages.
Norco also has the much more expensive
NORCO RPC-4020 4U Rackmount Server Case
but this has some cooling problems because of the orientation of the HDD SATA plug circuit boards.
Anyway, there are various other options but they are all too expensive or poorly designed. Paying a premium for drive carriers for something that really should almost never be removed seems absurd to me. I had thought about placing drives vertically so you could run the cooling down the length of them and the cabling would easily stay out of the way. If it's on rails it would be a simple thing to slide it out to get to the top for drive removal. And then via TUAW comes the Backblaze Pod. Clouds parted, angels sang. It was like someone was reading my mind! And they actually put the details up! 45 hard drives in 4U...wow! Cut one row out, make it more shallow and you have the perfect Unraid setup.
The only problem is that the SATA multipliers are a custom design. Well, so is the case but that could be built. The SATA multipliers are key to making this work and they would have to be sourced from somewhere.