I've always had an external drive that (was) a carbon copy cloned of my internal. This allows me to boot from this drive if there are issues with the internal drive. Does Time Machine (not time capsule, but time machine SW using an external FW-connected drive) allow you to boot from it, if the main internal drive fails? Can you rebuild your main drive from a Time Machine drive? I'm asking because I'm considering either RAID 1 or time machine, so I'm trying to understand how the sw works. Thanks.