While no drive made will exceed the current size supported you only need to read the Cnet Storage forum to find others that put all their files onto some external and then find they can't get at the external.
The moderators first question is "Where is the backup copy?"
Bob
I just replaced my desktop with an Alienware laptop. I have decided that I finally want to collect and store all of my data from my hobby family portait business in to one hard drive for storage. I found a 6 terabyte hard drive on a website that would allow me to dump all of my current data...but also allow me to grow the database. However in reading difference websites there are several challenges (or appear to be) using an external drive of this size. I would appreciate any insight.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic