I have a 2009 MacPro with an OS/apps main drive, and internal Data drive, and Firewire external backup drive . Time Machine points to the backup drive (partitioned for main and data), and SuperDuper clone/copies to it at night. At occasional and upredictable times, while I'm working, the backup drive spins up. The Mac Pro waits. The TimeMachine icon is not turning. Not sure why this happens, but its very frustrating since I have to stop and wait for the Apple 'pinwheel' to stop before I can continue what I was doing, or typing. Any ideas for stopping this?