Wouldn't be possible to just stack them in custom/modified racks, connect them to the tape and custom switch? Then get very cheap servers to switch through them? The hard drives don't generate much heat anyways so only basic ventilation would be needed. Using enterprise servers for Glacier sounds like an expensive luxury. Most discs would be mostly offline anyways (small amount of changes) and I bet more than a half discs would be used less than once a week so cost of. Then if you want to increase speed of the whole structure put 1u server with 4 x 4TB SATA3 discs in Raid10 for caching the most used/changed parts, connect server to 1Gbps line and you are all done on budget. The cost is just 1 simple server, modification to racks (that would cost really small money), tapes for discs and custom hdd switch.