You can get a seat post clamp with integrated threaded bosses that you can attach the top part of the rear rack to. This might be the best solution if your frame geometry is reasonable. For the lower clamping point, something on the quick release would be my preference, see the Tubus model that was mentioned above, but these also don't work with some shapes of frame tubes around the QR, and you'll also have to choose a rack & mounting method that doesn't interfere with the disc brake.
If it's your first tour and you're camping then you'll probably need more capacity than just a rear rack. It's not until the 2nd or 3rd camping tour that people figure out what things are important and what is not and can limit their amount of stuff to only need a rear rack, which would be what I would recommend. Don't use a backpack if you want to be comfortable on the bike for more than an hour or two per day - backpack cause all sorts of neck and shoulder pain for most people, plus they make your back too hot.
Lastly, I would never want to tour with hydraulic brakes because I can't maintain them fully while on the road - upgrade to a nice pair of Avid BB7 cable-operated disc brakes, learn how to adjust them before you go, and bring spare pads.
Last edited by Chris_W; 01-22-13 at 12:33 AM.