Originally Posted by howell_jeep
I just read up a little on what RAID is. I understand that depending on what RAID I want, I would need to have between 2-4 drives. They all need to be the same capacity and have the same specs, right?
I don't understand if I need the NAS for it to work? I don't want it to be available on the internet or home network.
With traditional RAID, you're stuck with the lowest common denominator. i.e. if you have 1x100G and 1x200G in a mirror (RAID-1), you only get 100G of usable space (100G is used for the mirror, 100G is forfeited). If you have 1x100G and 2x200G in RAID-5, you get effectively 200G of usable space (100G is used by parity, 200G (100 per drive) is forfeited)... in comparison 3x100G in RAID 5 yields 200G usable.
Drobo (and I believe Synology, maybe others) have a pseudo RAID that allows you to put disparate drives in, and it comes up with a protection strategy to use as much space as possible on the drives, while still protecting the data via mirror or parity.
My recommendation would be to put it on your home network, so it backs up independently of your OS, but Drobo has a 5D model that can be connected via USB/thunderbolt.