Glenn bought a 4TB hard drive so he could back up stuff and then move it to the cloud. But he's been told that he can't upload an entire image using Mac. Leo says that a more efficient way to do it is to have two hard drives and bring one off-site. Maybe to home or to work. Then swap them every other week. Leo also says that Fuse for the Mac will let you see other file formats on the mac, like NTFS, and use that to back it up.
From ScooterX, Costco has a Seagate External 8TB for $150.