symptoms of slow db server or webserver ?

I currently have 1 mysql db server, 2 php/apache webservers, and 1 image server for hosting one site. The image server is doing fine, but the other servers are hanging around a load of +/- 10 at peak times, and the webservers sometimes even jump to 20-30 load now and then.

I assume that there can be a lot of action-reaction load situations between db server and webserver. A db server can be running slow wich makes the webservers pile up apache processes for all new incoming connections while holding the excisting connections up for the slow db server, and therefore slowing the webserver down. But a slow webserver can also be slow in performing mysql queries on the db server, therefore needing too much resources from the db server, and as a result the db server will be running slow too.

Currently I'm not sure wich of my server types could be the real bottleneck, and wich are just slowing down because the others are slow too.

I'm mostly looking at mysql process list, mysql-slow logs and mtop for db server. And top and apache server status for the webservers. But its a lot of data sometimes, and hard to get the right conclusions from it.


So, are there any techniques, programs or checklists that can make me find out wich of my servers are the real cause of everything slowing down a bit at peak hours ?

 

 

 

 

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