I need a External HDD for backup Mac and store videos onto it. I don't know what size I need and what kind is best? I have my iTunes Library on my Netgear Ready NAS Duo v1. I thinking of moving it over to external HDD. My Library is not so big it only under 40GB. I usually edit Holiday videos and learning After Effects from time to time. I am leaning towards WD passport just because they are cheaper I can get 2x1TB for £138.90 on Amazon. Will the time machine auto detect my external Hdd to use as Backup? I am curious about the size of videos and moving them between the external HDD and into Adobe Premiere Pro CS6. Most of people recommend me to buy a thunderbolt version of HDD because it transfers faster. They are still expensive. Recommend me guys.