My Pugsley in Wadi Rum earlier this month.
There are 5 (count 'em) 1-liter water bottles on the frame itself, which leaves the entire frame bag free for food. The handlebar roll is pretty much just a quilt, a few clothes, and a tent (footprint and fly only), plus odds and ends in the pocket bag. The gas tank has snacks and the normal contents of my pockets (phone, wallet, passport, Leatherman). The saddlebag has the rest of the clothes (I brought a lot for that trip, expecting cold nights) and a Thermarest sits on top.
I also had a daypack, which I could fill when needed with another 3 liters of water, and more food. I never really needed as much food as I had, but I was glad for the extra water capacity. I also skipped a potset and stove on this trip, and some bike tools as I was riding with a couple other people and mooched off their pump/multitools.
For warmer-weather trips I'd save a bunch of space by bringing less clothing - in particular, my fleece and bike pants were bulky. I'm planning another several-day outing this next week and expecting much warmer weather so I'll have to see if I can consolidate things to the point of not needing a backpack.