Setting up a cluster is just one of the responsibilities of a Hadoop administrator. Once the cluster is up and running, the administrator needs to make sure the environment is stable and should handle downtime efficiently. Hadoop, being a distributed system, is not only prone to failures, but is expected to fail. The master nodes such as the namenode and jobtracker are single points of failure. A single point of failure (SPOF) is a system in the cluster, if it fails, it causes the whole cluster to be nonfunctional. Having a system to handle these single point failures is a must. We will be exploring the techniques on how to handle namenode failures by configuring HDFS HA (high availability).

The namenode stores all the location information of the files in a cluster and coordinates access to the data. If the namenode goes down, the cluster is unusable until the namenode is brought up. Maintenance windows to upgrade hardware or software on the namenode could...