MySQL eating memory... server overload

[dazmanultra]

Basically MySQL seems to decide to eat loads of memory, randomly. This causes the server to use swap, and then it's thrashing all over the place and services start failing.

Any ideas?
(see the attached image)

[chirpy]

The image you attached is pretty much meaningless. You need to establish which MySQL database and what lookups are causing the problem with MySQL on your server. There is good information on the MySQL site to do this type of thing and information about how to do MySQL tuning if you haven't done any of that. A starting place could be WHM > Show MySQL Processes