I will probably be getting one as a back up of my 2010 macbook pro hard drive through time machine or some other app. Should I get a bare drive & enclosure & put it together myself? or just look out for a deal on a pre ready hard drive? my mac's hard drive is 500gb, should I stick with this size for a backup? or get something bigger? what would be the best app for this backup? time machine? I have never used time machine, & also how would I format the drive? I would want it so if I had to go to a new mac, I could just copy the backup hard drive contents, with all my apps without having to go through all my software to reinstall. also, would this backup have to be plugged in all the time & running? or just when I do back ups?