title: Mongo Server Status - "Resident" memory
body: <p>After starting Mongo via <code>mongod</code>, I ran a Mongo query that took <strong>300</strong> seconds. Calling <code>db.serverStatus()</code> on my "admin" db showed Mongo having <a href="http://docs.mongodb.org/manual/reference/command/serverStatus/#server-status-memory" rel="nofollow">resident</a> memory of 1 GB. The docs explain that "resident" memory is the amount of physical disk/RAM that Mongo uses. </p>
  
  <p>Then, I re-ran the same query, but it took <strong>8</strong> seconds. Looking at the <code>resident</code> memory this time, I saw 5 GB.</p>
  
  <p>The large increase in RAM, I believe, helps to explain why the query time shrank from 300 to 8 seconds, but why did the resident memory jump so quickly?</p>
  
  <p>Is there some type of "warming" step recommended to prepare Mongo so as to avoid 300 second queries?</p>