When you backup your OSx with Time Machine does the external drive need to be completely empty and dedicated as a time machine backup or can you backup an OSx onto a 2TB drive that already has 1TB used on it? I have no interest in doing continuous backups with Time Machine, just one. I just reinstalled my OSx and all my plugins so I want to do one backup of it with everything installed clean before I move forward and start working. If so, does anyone have a good guide on doing a one time time machine backup then disabling backups so it wont do another one? Im sure its easy but ive never done it before.