My problem is the same as in the question:
https://community.f-secure.com/t5/Business/slow-disk-while-scanning/td-p/50403
The solution to that one is wrong. He did not ask about limiting CPU usage, but limiting the IO usage that the F-secure real-time scanning is taking. It renders my high-end macbook pro useless (even though 97% of CPU is idle and _no_ programs are running) while it is doing real-time scanning to an external hard drive. Is there a way to exclude the real-time scanning from scanning external hard drives?
