It appears that having a hard disk larger than 2Tb violates certain assumptions which the computing world holds dear to its heart. Lots of things one takes for granted stop being so, and all sorts of other things get violated. For example, fdisk doesn't work any more, and it refuses to explain why not. Given that I can buy a 1Tb disk in the high street, I seriously hope the software world catches up with the game. I will get some sleep when I manage to get an operating system to run on a 3.4Tb disk.
For the curious who don't already know, the classic "DOS" partition table format is limited at 2Tb, and one must use GPT or BSD or something similar instead.