title: Hadoop version layout error
body: <p>I am getting this error in one or two nodes in a Hadoop cluster, where rest of the nodes are running fine:</p>
  
  <pre><code>ERROR org.apache.hadoop.hdfs.server.datanode.DataNode: java.io.IOException:  
  *********** Upgrade is not supported from this older version of storage to 
  the current version. Please upgrade to Hadoop-0.14 or a later version and 
  then upgrade to current version. Old layout version is 'too old' and latest 
  layout version this software version can upgrade from is -7.
  </code></pre>
  
  <p>Any idea how to fix this problem, without losing the data?</p>