Western Digital Purple 2TB for VIP722k?

Would it be a good idea to use a WD Purple 2 TB hard drive in an external enclosure with the Dish Network VIP722k? (I think there's a "K" in there anyway). Not getting it just because it's geared towards DVRs (well..the marketing hype machine says 24/7 surveillance DVRs. Television DVR counts - right?). It was best deal I found on 2 TB drives I have found, which is why I leaned toward it.

Also, what is the file format on an external drive on a Dish DVR? Can they be backed up and archived,...

Western Digital Purple 2TB for VIP722k?