The short answer in my opinion is no - I've got as mentioned previously in this thread and in my signature a Seagate 750Gb connected to my HR20 and I've had it up to 80% capacity which believe me a LOT of HD Programming. I haven't noticed any performance hit at all. That said I have heard of some people here that are using external RAID units that offer as much as 3Tb of Storage. I'd be very curious to hear their experience on this. They more than anyone would be able to shed some light on this. BTW - I should mention that everything that I've recorded has been HD Content which includes national, local and OTA so MPEG 2 & 4 but SD whatsoever. I've got 2 SD Direc-TiVO's for that. I will eventually retire one of the TiVO's and get another HR20 to replace it. Probably as soon as the new bird goes up which should.