SamyGO

I think this is related with your HDD partition format. Not related with HDD itself.

Okey it's easy to test. Format 3T disk with FAT32 or EXT3 and look what happens. I bet it will be recognized.
(FAT32 has 2TB limit so test it with 2TB partition.)

Yes, TV cannot recognize GUID/GPT partitions.
Might arris69 could add support for it by compiling new kernel modules.