For many years I've been using cloning as my main backup strategy for both OS and Apps. Initially it was necessary to use a Firewire interface to boot from an external drive, but I seem to recall reading that some macs can boot through USB from an external. I've just had an external go south and it's becoming more difficult to fine external Firewire drives. I'm cloning a Macbook 4,1 and I'd like some feedback concerning the interface required to boot the MB from an external. Obviously USB would be considerably slower, but at least I can purchase an external USB at a reasonable price. Any and all replies would be much appreciated. Thank you.