On my webservers I always use an installation of munin, to track events on my servers that happened while I was sleeping. Today, I saw that around 6 in the morning there where a huge increase of mysql requests, around 6.5 times more than the average count of requests. Also the cpu usage increased that time around 7.8 times over the average. That problem last for about 10 minutes. So I had to investigate it a little bit.