Drupal’s modular setup allows for different datastores to be integrated as modules, this allows sites to store different types of Drupal data into MongoDB. You can choose to store Drupal’s cache, session, watchdog, block information, queue and field storage data in either a standalone MongoDB instance or in a MongoDB Replica Set in conjunction with MySQL as the default datastore. If you’re looking at clustering your entire Drupal setup, then see this blog on how to cluster MySQL and the file system.In this blog post, we are going to integrate our existing Drupal installation which runs on MySQL with a MongoDB Replica Set. We are running on Drupal 7, which is located under /var/www/html/drupal on server 192.168.50.200. It has been installed and configured with a MySQL server running on the same host and Drupal is running and accessible via http://192.168.50.200/drupal.