It looks like this has been asked, but I'm not sure what the answer is. Can I place 2 -2TB drives in a dock with Raid 1 controller, USB 2.0 or 3.0, and have it work with a 622 or 612? Supposedly this looks like a single drive. I just lost an older, smaller HD, and my other two 2 TB. are getting long in the tooth. Is there any other way to keep from losing stuff?
If the controller successfully makes it look like exactly one, normal, USB disk, then I think it would work. Please let us know if it actually does! (And which controller/box you used.)
BTW RAID 1 is mirroring - everything copied to two drives so it doesn't decrease reliability like RAID 0. (Although it probably won't save you from user errors and SW glitches like a true backup can.) The only thing that would keep me from doing this is the question of whether old TV is worth the effort/expense. But if the OP documented a successful recipe, then that lowers the "effort" quite a bit.