I've been considering building out an open source private cloud utilizing mostly used equipment. One of the few pieces of equipment that I'm considering to purchase new is the disk subsystem. Here I'm going to go into that consideration, no technical details only high level technical considerations (sorry).
My requirements are simple. Large cheap disks, seamless automatic disk failure recovery, full redundancy, accessible by older commodity hardware, and since rack space is a ongoing cost, I'd like the overall footprint to be small.