kernel_task writes huge amounts of data to disk (> 1TB) - how to diagnose?
I had the same issue on my 2010 MacBook Pro.
The fix for me was to clean out the dust from inside my laptop. I removed the fan (just requires unscrewing it with a special screwdriver, like the type for installing a hard drive) and there was a giant amount of dust blocking the airflow.
Kernel_text helps regulate the computer temperature. It was trying, but the fan couldn't do its job. After this fix, I went from 500 GB of kernel_text disk usage within a few hours of computer use, to less than 2 GB.
Interestingly, this also seemed to fix the issue of disnoted and sharedfilelistd processes using too much CPU.
However, my computer didn't have massive disk usage from the CrashPlanService process, so you might have a different issue.