As far as i can tell, this DVR functionality is constantly on during gaming? If so, it would cause wear out on SD card and slow down the game quite a lot in particular during loading where there would be constant writing to the SD card as well as game level loading. Doing it in a rolling buffer in ram via hardware encode is probably the reason why 30 seconds is the default (8mbs - around 1mb per second encode) would require 32mb of ram space