title: where is data stored in hadoop
body: <p>Though I have understood the architecture of hadoop a bit , I have some void in understanding of where the data is exactly situated.</p>
  
  <p>My question is like " Suppose I have large data of some random books .. is the data of books stored in multiple Nodes previously using HDFS and we perform MapReduce on each node and get the result in our system ?</p>
  
  <p>'OR'</p>
  
  <p>Do we store data some where in large database and whenever we want to perform the MapReduce operation, we take the chunks and store them in multiple Nodes for performing operation ?</p>