How "idle" is an idle Operating System? More specifically, how much I/O is going on when a system is left for about 3 hours doing nothing?
In my test, I rigged up a modified version of QEMU to dump out all I/O block read/write activity. I then installed two Operating Systems for comparison: Windows 7 RC and Ubuntu Karmic Alpha 3. I then left the systems to sit around and be idle for about 3 hours and then afterwards I examined the I/O activity. I then plotted the cumulative block read/writes for both operating systems so one can see the total block I/O over the 3 hours.
If you peer carefully right at the bottom of the graph below, you can see that Karmic flushed some blocks out to disk, and then essentially that's about it - no real I/O activity. As for Windows 7, it seems to delight in rummaging around, doing a load of reads and even more writes:
It's quite shocking how much Windows 7 wants to keep the system busy, and this was a clean install with NO virus checker running in the background. Naively, I suspect Windows 7 is defragging it's filesystem (something you don't need to do on Linux), but I didn't want to poke around and interact with it while running the test. If it is sneakily optimising the system behind one's back while idle, I hope it does not do it too often.
So, any Windows 7 user out there with Solid State Drives (SSD) needs to be aware that an idle Windows 7 will wear out their SSDs quicker than Ubuntu Karmic.