Instead of Time Capsule or a NAS, I've decided to just use an external Firewire 1TB external drive to backup my MBP with 500Gb drive. Does Time Machine run 100% in the background? I'm concerned that I may want to disconnect my external drive at a time when Time Machine running a backup. How do I know when Time Machine is backing up and when it's finished? Are you expected to wait for Time Machine to complete before disconnecting, or are there some smarts built in to Time Machine to account for this?