title: recommended pool size to set for mongo from a rails app (nginx, mongomapper)?
body: <p>our app runs on rails 3.2.12, mongo 2.2 (will migrate to 2.4), mongomapper, and uses nginx + passenger. </p>
  
  <p>if we're on a VPS with 5 GB of RAM, what's the best way to determine the optimal pool size for our application, and where do we set it?</p>