Kernel_task disk I/O?

Question

I've noticed that no matter what I'm doing, the kernel_task appears to write to disk (~5 MB/s) either constantly or in aperiodic burst. It appears to read about 1/200th of this rate. Spotlight is not indexing. The MDS and other tasks aren't using any appreciable CPU cycles. The machine is basically idle except for this disk I/O.
My questions are:
1) what the **** is the kernel writing to disk?? (Or how can I find out?)
2) why?
3) is this normal behaviour?
4) can I stop it? (The constant disk writing sound is pretty annoying after a while.)
5) if it's possible to stop this I/O, what are the possible consequences?
I have a quad-core Mac Pro running 10.9.1, 16GB of RAM, two LVM-ed 1TB HHDs and a 2TB external containg a fully bootable back-up managed by ChronoSync. I have a few cron things:
* */2 * * * /usr/bin/purge
0 1 * * 1-5 rsync -azu -e ssh ...{snip}...
0 13 * * 1-5 killall rsync
0 1 * * 6-7 rsync -azu -e ssh ...{snip}...
0 5 * * 6-7 killall rsync

Answer 1

For the moment at least, I think repairng my disk permissions (with Disk Utility) may have fixed whatever the issue was. The machine is has been reading and writing between zero and KB/s for several hours now.