Sometimes the server is very slow and needs a lot of time for serving the requests.
iotop shows a disk read rate of 1-2 M/S on average for some minutes (which is not that much actually), after that the server is very fast again.
while being very slow the wait rate is about 60-90% according to top.
All mysql caches are more than OK according to mysql tuning primer. So I don't know why the mysql server does so much disk reads. Is there any way to find out what causes so much I/O read in mysql?
I have to say that it is a virtual server, so could it be that another customer is using the whole I/O capacities?