title: Name Node stores what?
body: <ol>
  <li><p>In case of "Name Node",
  what gets stored in main memory and what gets stored in secondary  memory ( hard disk ).</p></li>
  <li><p>What we mean by "file to block mapping" ?</p></li>
  <li><p>What exactly is fsimage and edit logs ?</p></li>
  </ol>