title: Capped Collection in mongodb issues
body: <p>I made an analysis on capped collection, I found that there is no performance improvement in capped collection.
      I created a collection named test1 with 20,000 data, I did copyTo test2 with same data which is capped true with data size specified. I gave the following queries to examine the performance</p>
  
  <pre><code> db.test1.find( { $query: { "group" : "amazonTigers"}, $explain: 1 } ).pretty()
  
  
   db.test2.find( { $query: { "group" : "amazonTigers"}, $explain: 1 } ).pretty()
  
   Both result in the same response time as 124ms...
  </code></pre>
  
  <ol>
  <li><p>More Over, I dont understand how the capped collection works???</p></li>
  <li><p>I read through lots of blogs, But am not able to find the correct working principle of mongo capped collection. </p></li>
  <li><p>I read through the disadvantages of capped collection, Its given like we are not able to use $set and $push in it. Is there any other disadvantages there in capped collection for the specified collection entries???</p></li>
  </ol>
  
  <p>Regards,
  Harry</p>