What would normal disk usage considered to be in the usage window?

[Digitopian]

After installing 8.0.1 I began working on a session that was atypical for me in many ways. It was my first time using strike as the drum track, first time using multiple instances of eleven, and first time in a while doing a session at 88.2khz. Also I believe it was the first time that i chose to record at 64 hardware buffer setting, foregoing recording in low latency mode. After slapping on some plugs to get a quick idea of how it things might sound mixed I inevitably ran into a cpu error. Not surprising considering this was a session of firsts.

At this point I decided to continue the session with the usage window up to get an idea of how various things were effecting the cpu usage and noticed that cpu usage seemed a bit high(although I understand why this is) but also I noticed that the disk usage was higher than I had ever seen it. Normally I have never seen it above 10% but i should state that I generally don't work with the usage window open as i generally don't really run into many usage type issues.

This peaked my curiosity and i decided to open up some session that were fully mixed and edited as well as a few sessions that have a pretty high track count. What i noticed was that on many of my sessions (particularly the ones with high track count) the disk usage was showing as high as something like 27% maybe more. So now I am even more curious. Is this normal? Have I been using Protools for ten years without noticing this, or is this a sign of something else. The drive that I'm recording to only has about 40gig out of 500 used. Not sure if that matters but I figured I'd throw that out there.

Sorry to be so long winded but i couldn't really think of a concise way of asking the question in the title of the thread. So what do my fellow duc'ers think?