title: Understanding the Hadoop File System Counters
body: <p>I want to understand the filesystem counters in hadoop.</p>
  
  <p>Below are the counters for a job that I ran.</p>
  
  <p>In every job that I run, I observe that the Map file bytes read is like almost equal to the HDFS bytes read. And I observe that the file bytes written by the map is the sum of the file bytes and hdfs bytes read by the mapper. Pls help! Is the same data being read by both local file and hdfs, and both are being written to the local file system by the Map Phase?</p>
  
  <pre><code>                Map                        
  </code></pre>
  
  <p>FILE_BYTES_READ     5,062,341,139        </p>
  
  <p>HDFS_BYTES_READ     4,405,881,342       </p>
  
  <p>FILE_BYTES_WRITTEN  9,309,466,964   </p>
  
  <p>HDFS_BYTES_WRITTEN  0          </p>
  
  <p>Thanks!</p>