2 questions from a noob

1) I'm trying to decide on what size drive I should get
and would like to know if for example I bought a 200GB drive
how much would I be able to use? in other words once formatted
how much of the HDD becomes unusable?

2) what's the best way to backup games?
direct via PS2 or via PC then inject into the HDD?
cuz the PS2 DVD drive may not be the most reliable..maybe

Thanks

dirvecley installing from ps2 or from pc should get the same end resolt

direct pc to hdd transfer is faster, dose not deminish the life of your ps2 lazer, and is the ezest to install game that required patches so I would recomend that