One of the most common suggestions to bloggers who use shared hosting is that they will be much better off with a VPS or a dedicated server. I agree in principle; however, this doesn't mean the server will run smoothly without a bit of tweaking.

I'm currently in the process of moving several WordPress blogs from a dedicated server to a VPS. After moving five or six blogs, I noticed the server was slowing to a crawl, with high load after just a week of uptime. None of the blogs are particularly busy. What would solve this problem?

WP-SuperCache

A quick way (no pun intended) to speed up WordPress is to install WP-SuperCache. This is the first thing I tried, but I didn't notice much of an improvement.

Server Security

Security configuration changes may help if the slowness is caused by people exploiting weaknesses on your server. But this didn't help either.

php-apc

The trick that worked for me was to install php-apc. Assuming you've got access to the command line and it's a Linux box, installation is simply a case of issuing the following command:

sudo apt-get install php-apc

This may vary depending on your Linux distro.

Result

Installing php-apc has reduced the server load from a peak of 30 or 40 right down to a peak of 0.5, and the server has been happily running for a few days without any major problems.

Photo by Mykl Roventine: Out & About