I have recently bought a bunch of enterprise-used Hitachi 2TB drives. They all work fine, and have typical numbers present in S.M.A.R.T., which is around 30 power-ons and 45.000 hours spinning. This is how they normally show up:
Disk showing it's correct size of 2TB:

But here comes the kick: one of the bunch is odd, as it only shows 1TB:

This particular drive has a sticker that says 2TB, it's from the same series as the other drives. Notice that the name of the drive also doesn't contain the word HITACHI and Transfer Mode is detected as only SATA 300. BIOS also sees it as 1TB. The drive behaves normally otherwise.
Why is this and what can be done about it? Is there a firmware update that needs to be done for the drives?