Or could it be that half a gig was just a figure he came up with to demonstrate the (ostensible) difficulty in doing a proper backup ?

Well, half a gig is trivial to backup. Half a terabyte is not. Assuming you meant to say 500 gigs, then yes, there is difficulty, but it's not uncharted territory. He had two xserves -- perfect for replication.

It's not even close to uncharted territory. You can walk into any Apple store and buy a 1-terabyte backup device off the shelf.

OK so it won't handle your databases properly but that's not the point; 500G is not a troublesome amount of data these days.

No the point is backing up a 500G database is difficult, but not unpossible. Sorry if that wasn't clear.