It is very possible to scale WordPress to support multiple sites. WordPress.com, for example, has over 13 million. The trick, when it comes to performance, is to:
- Make sure your server can handle it
If you’re on a shared hosting system, upgrade to a dedicated server (or many). If you’re running 170 blogs, you should have already done this. - Use caching
Every time a page is viewed, WordPress will go back to the database to re-build the page dynamically. If you have a lot of traffic, this can be very bad for performance (i.e. a lot of sites with a little bit of traffic = one site with a lot of traffic). - Use multiple databases
Just like you want to try to split your files across multiple servers to ease the load on one system, you want to spread your database system out as well. There are several ways to do this … try Googling for one or two.
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