title: Hadoop Block Count Calculation
body: <p>We are running a Hadoop cluster with replication factor as 3 and block size as 64MB. We just wanted to know the best way to calculate/run command for seeing actual data size that resides across the datanodes.<br>
  Also, we tried using <code>hdfs dfs -du -h</code> and <code>hdfs dfs dfsreport -report</code>, but what we noticed was that if our disk size is 12TB:<br>
  a) The first command would show me the data usage to be close to 500GB<br>
  b) The second command would show the data usage at 11.5TB.  </p>
  
  <p>What is the reason for difference that we are missing here? Any help would be great!</p>