I got nearly two TB of space that I back-up and got a 2 TB external HD that's the back-up. When I need more space for Time Machine, would it be possible to have two 2 TB external HD's and tell Time Machine where to back the stuff up to? For example, having the stuff from the System HD back-up on one external HD, and stuff from another Hard-drive back up on another external hard-drive. Would it help a hard-drive last longer if you only have it powered on when you use it, or does it make no difference always being on? Would it help to regularly run DiskWarrior on it, before it shows any hint of dying, or is DiskWarrior just for trying to recover a hard-drive that's showing hints of dying?