[T2DMan]

When the servers get overloaded because you are getting so much traffic from the fab SEO / SEO vBulletin, what do you do?

Move along the scale:

• shared server
• virtual dedicated
• dedicated server
• dedicated with more ram, disk drives, faster cpu
• dedicated with separate server for mysql database
• dedicated server with mysql database replication on multiple servers
• load balancing multiple servers, with separate mysql server database
• load balanced servers in different datacenters

Alongside this, is the tweaking of the scripts including possible caching of pages rather than them having to be generated from php script.

With load balancing, you have to be careful that you don't introduce multiple url's for the site - don't have www1.bla, and www2.bla. Check out the load balancing article on webstream. It describes what I consider the best solution with a intellegient load balancing system that checks the load of each server before it sends traffic to it. Means that you can add other servers into the mix and get the optimum load across each. Everythingsolaris has another good load balancing article.

Wikipedia also provides good discussion on the types of web hosting available.