I understand that Time Machine can back up from an internal + external(s) to another external. I have a 750 internal and a 750 internal and am looking to offload my media to the external and then get a 2TB external to Time Machine both drives to. My 750 external is FW800. Am I better off getting a 2TB USB 2.0 or a 2TB FW800 as the Time Machine drive. I didn't know if the daisy chain aspect of 2 drives and TM reading one and trying to write to the other is a potential bottleneck/data conflict issue or if it is better to read from the FW800 drive and write to a USB drive. The USB solution is cheaper. But I was curious about the technical aspects of it mostly.