Re: Performance of BuddyPress on WP versus WPMU
@techguy There are a couple of considerations.
First, @travel-junkie is right that you don’t have to do too much to switch MS on in WP 3.0. However, once you’ve switched to MS you can’t go back.
Second, WPMU(MS) performance is really just a function of how many blogs you’ve got. If you install MS and still only run a single blog, resource usage will be practically identical to a single-WP setup. As you increase the number of blogs (and, by extension, the number of db read/writes), required resources will increase in a way that is a little bit steeper than linear. In other words, going from one blog to five blogs (each with the same amount of traffic and activity as the one blog) will require just over five times the memory (the “just over” is because of inefficiencies introduced when you start to get a lot of blog tables in the database).
I don’t have a lot of numbers to back me up (i’m a noob), but at least in terms of DB hits and memory usage (typical bottlenecks for a WP installation, I think), adding BP is more resource intensive than adding a couple of extra blogs. Think of all the dynamic stuff that gets loaded with every BP page load. Plus I would wager that introducing BP means many more page loads per visit, given the nature of the content.
I’d love to see someone with some serious sysadmin chops do a real study of BP performance, so that people will have a nice basis for decision making when looking at potential hosts.