Okay, so I have a 12" powerbook, and i like downloading lots of things...you know.... anyway, I obviously don't want to put it all on the drive in my powerbook, because it's already dying, and I don't really want to push that. I built an external box out of an electronics project box, put a couple switches on it, and put some drives inside it. Put some IDE to USB 2 converters inside, a powersupply, and now I have a 700 gig external setup. Anywho. The problem is, I want to do things like leave my computer on all night, with my drives plugged in, and download straight to them. I have a usb hub installed inside the box, so it's all going into one usb port on the powerbook. What I want to know is, how intensive is this on the disk inside my powerbook? Does OS X write data do the disk, and then transfer it out, does it write it to the computer's bus, and then send it out straight through usb skipping the internal drive altogether? Or something else?