Is this strange? Memory usage while compressing...

I have a mac pro that mostly acts as the file server for my small video post-production facility -- it has a 4TB internal hardware RAID, 2x2.8 xeons, and 10gb ram, hooked up by gigabit ethernet to a number of iMac edit stations.

I occasionally use this beast of a computer for rendering for obvious reasons. Today I'm all alone (no editors, whee!) and I'm using a Compressor queue to encode some full-res videos. I've always found memory usage to be very strange while doing this and I figured I'd ask if anybody could give me some answers.

I have 8 instances set up in Qmaster, so all 8 cores of the computer can be used for compressing (this is a pretty standard setup). The thing is, more than 2/3 of my RAM is marked "Inactive" in activity monitor. I always figured this was for the file server (and the whole reason I put 10gb in a file server) -- so it has a large buffer in case the RAID can't keep up when I have 8 editors working hard simultaneously. But nobody's here today! Nothing is going on over the network. Still, my Compressor processes only get about 100mb of RAM each. Pathetic!

Some light googling generally reveals the answer "don't worry about inactive RAM, OS X knows what it's doing" and I'm inclined to believe that in most cases. In this case, though, it feels like a mistake. I've even un-mounted all volumes on the server from the workstations. Since I submitted the job to the queue at High priority, I'd expect it to actually make use of 10gb RAM to render!

Does anybody have any insight? Screenshot attached.