HP have been running variants of this MicroServer offer for a year or so now. They’re really really good value. The CPU is virtualisation capable. They’re RHEL certified. Besides the 4 drive slots, the motherboard has a USB socket on it so you can run the host O/S on that & have the 4 drives in full 3+1 RAID5.
Most of my work colleagues have at least one. I’d say a majority have more than one :)
I use mine as a backup for my main server, with 4 x 1.5TB drives in RAID5. It’ll run backups of all my VM’s, including my VM that runs my NFS shares for music & video. The only other thing i needed to add was a second NIC.
These would make an ideal NAS. They’re whisper quiet. The build quality is excellent. The fan draws air directly over the drives so they’re unlikely to overheat.
One note of caution that a friend got bitten by. HP dealers are excluded from this offer. Buy from somewhere like EBuyer that’s actually advertising the cashback offer.
+1 to what Cougar & others have said about RAID not being a backup. The other thing i’ll add is whatever backup strategy you chose, regularly test that you can recover from it.