I recently bought a refurbished HP DL385 server at auction. It turns out that it takes SFF (Small Form Factor) disks and has the ability to take 8 hot-swap disks (not bad for a 2U server).
The machine supports SAS disks and S-ATA disks as well. So the next thing to do is to buy a bunch of S-ATA disks for it.
When I got the machine it reported that the battery for the write-back cache on the RAID controller could not be recharged and needed to be replaced. Apparently this is a firmware bug and I can fix it by upgrading the firmware on the machine. Of course I need to buy some disks so I can do an OS install first.
As an aside it’s amazing how cheap some of the Opteron servers are at auction nowadays.