I know that busy phpBB forums can be resource intensive, but haven't run one myself, and can't find any sort of quantification of that. How do I plan hosting needs given an expected load of users/logins/posts/etc? My current setup won't be adequate, but I have no idea how much more I'll need.
It seems like this must have been addressed before but any query with the terms 'phpBB hosting' has been SEO'd to death and turns up nothing but ads for hosting services.
The first step in improving the performance of any PHP code is to install a PHP accelerator, like Alternative PHP Cache (aPHC, included by default in PHP 6) or Zend Optimizer (there are a bunch of them around).
The second step is to use a profiling tool and find out where the bottleneck is; it could be processor, disk, or even bandwidth. Without profiling you will never know for sure. Zend Server includes a performance monitors that gives you detailed information about how long the code takes to execute; of course, there are many other profiling tools you can use, like Xdebug (also a debugger).
