I use two G-Drives which came formatted for Mac. I store everything on the 2TB drive and use the other (4TB) to back everything up (including the HDD of my MAc book Pro) using Time Machine. I keep the second one at my office and bring it home for backup once a month or so. The primary is striped (Raid 0) which makes it exceeding fast but twice as likely to fail (since if only one of the two drives fails I loose everything). The Backup is Raid 1 for redundancy but half the capacity which is OK since it was originally twice as big. So Both have an effective 2TB capacity. I am getting close to capacity so later this year I will probably just buy two larger drives, maybe a 4 and and 8 and set up the same system.
