title: Hadoop Cluster Failover
body: <p>I have some questions about the Hadoop Cluster datanode failover:</p>
  
  <pre><code>1: What happen the link is down between the namenode and a datanode 
     (or between 2 datanodes) when the hadoop cluster is processing some data?
     Does Hadoop cluster have any OOTB to recover this problem?
  2: What happen one datanode is down when the hadoop cluster is processing 
     some data? 
  </code></pre>
  
  <p>Also, another question is about the hadoop cluster hardware configuration. Let's say we will use our hadoop cluster to process 100GB log files each day, how many datanodes do we need to set up? And for each datanode hardware configuration(e.g. CPU, RAM, Hardisk)?  </p>