HA configuration is backward compatible and works with your existing single NameNode configuration. The following instructions describe how to set up NameName HA on a manually-installed cluster. If you installed with Ambari and manage HDP on Ambari 2.0.0 or later, instead of the manual instructions use the Ambari documentation for the NameNode HA wizard.

	Note
	HA cannot accept HDFS cluster names that include an underscore (_).

To deploy a NameNode HA cluster, use the steps in the following subsections.