Any suggestions on how to implement a shared web hosting cluster with multiple CMS? In our case, we have 2 web servers attached to shared storage. If we want to host Wordpress, Drupal, and Joomla sites, would it be more prudent to have separate clusters for each CMS or can they all be installed on the same shared volume and just let the 2 web servers (running Apache) take care of serving up the pages regardless of which CMS was used to create them?
your other question contains the answers to the first part of your question.
While implementing drupal, wordpress and joomla all have their own performance issues, running them on the same cluster would be fine. As load increases, add more CPU, split mysql to separate clusters, etc.