Heres what has been tested and verified working :
1TB USB HDD,
4GB USB Memory stick(SanDisk Class 10)),
32GB USB Memory stick(SanDisk Class 10),
2GB micro SD(Transcend) tested on T1, T2 and Z7+.
Recording, playback, timeshift.. all fine..
with our test, we think it is not the matter of capacity of hdd/stick memory/micro sd, but matter of brand and quality of them.for the stick memory, below class10 is not recommended for recording and playback.