Used to be 3TB. Been hearing some people can get more now with TE4. Wanted to see if this is true with TE3 also. No, in fact with my tests LESS. I tested a couple TE3 Roamios with 4TB blank drives. Both TE3 Roamios formatted the 4 TB drives to only 284 HD hours which I think is less than 2TB? One of the Roamios I started fresh with a 3TB drive early this year. And it formatted the whole 3TB (that is the drive I am currently using, 477 HD hours). But now that TE3 Roamio only self formats the 4TB drive to 284 HD hours. Strange..................... I assume I could use MFST or MFSR to get full capacities on larger drives. But wonder why at least my TE3 Roamios format 4TB drives to less than 2TB now. Been "things" going on with TE3 this year, most not good............