[ekool]

Gabriel,

You should install mtop on your database server and see if you can tie any particular "database" activity to high loads on your web servers.

You have over 2.2 million posts. My guess is that when someone is searching your forums, you run into the very common table lock issue which causes your webservers to queue all connections... when they do this, they open many apache/php processes and just sit there.. memory use goes up and cpu activity goes up until eventually either the search query finally finishes and pages are served or your apache servers hit their queue/connection limit and start rejecting new connections.

My guess is that you are going to need to get the sphinx search hack working and once you do that, your webserver loads will go down as well.

First step tho, look at mtop. We ran into this issue recently and even tho the mysql server would shunt multiple hundreds of mysql queries into the WAITING state, the load never went high. However, it did have a direct impact on the load of the web servers.

Hope this helps.