Got a 2008 iMac with 2GB of RAM running lion. Need 3TB of external storage with on-site backup to guard against mechanical failure. Simplest is a live disk for the storage and use time machine to keep it safe, but it's inelegant. I'm looking at getting two fw drives and daisy-chaining them then using disk utility to whip up a soft raid but... I hear software RAID is maybe bad and possibly unreliable, so I'm open to dropping the price of a third drive on a raid enclosure to do the mirroring in hardware. My main question is, is a single drive usable alone? What happens if my mac falls over? Can these disks be plugged into another mac and still function? My secondary question is what happens when a drive fails in each case? Can you limp on with one drive in either case?