Configure HDFS Federation

An HDFS federation allows you to scale a cluster horizontally by configuring multiple namespaces and NameNodes. The DataNodes in the cluster are available as a common block of storage for every NameNode in the federation.

Ensure that you have planned for a cluster maintenance window before configuring the HDFS federation because all the cluster services are restarted during the process of configuration.
Verify that you have configured HA for all the NameNodes that you want to include in the federation.

You must associate every NameNode you want to include in a federation with a namespace. You can configure a maximum of four namespaces in a federated environment.

In Ambari Web, select Services > HDFS > Summary.
Click Actions > Add New HDFS Namespace.
The Add New HDFS Namespace wizard launches. The wizard describes the set of automated and manual steps you must perform to add the new namespace.
On the Get Started page, type in a NameService ID and click Next.
On the Select Hosts page, select a host for the additional NameNodes and JournalNodes, and click Next.
On the Review page, confirm your host selections and click Next.

On the Configure Components page, monitor the progress bars as the wizard completes adding the new namespace, then click Complete.

After the Ambari Web UI reloads, you may see some alert notifications. Wait a few minutes until all the services restart.

You can navigate to Services > HDFS > Summary to view details of the newly added namespace.

	Note
	If the process of adding the new namespace does not complete, then you must update the configuration properties of the NameNodes so that the cluster reverts to its earlier functional state.