Originally Posted by jefro
In a general sense the (sd)a and the (sd)b would be a clue to there being two complete physical drives. I never tried it but I guess it could be fooled or even mirrored. That would be very uncommon.
Not even sure about the 80 gig guess either. I'd have to ponder on that. I'd be thinking a 73G size.
They are most likely labeled as 80 gb drives. Even though you can store less data on it. In this case just over 73 gb.
It's that way with all hard disks since as far back as I can remember.
For example the hard disk in my laptop is a 750 gb model, yet it can only store 694.7 gb.
There is a nice explanation on this Wikipedia page
about this stuff