For static websites I'm using HAProxy (one master, several nodes with static HTML files on them). What services in addition would you recommend to allow WordPress sites to be hosted in the same way in terms of MySQL and files across the nodes changing.
Thanks for any advice/pointers.
Edit: I'm using Ubuntu currently with a standard LAMP stack, the reason why I need this is because as soon as one of my clients sites goes down because they are getting 1000's of hits is when they call me and I get shouted at.
@polynomial The data changes all the time (the main problem) the slaves need to be access really in a which one has the least load on it. MySQL is currently just a single server, serving the data to WP. We do know a little bit when sites will increase load, but there is not much we can do apart from add more ram and bandwidth.