As of this book's writing, the NameNode of the Hadoop stable release is a single point of failure. In case of either accidental failures or regular maintenance, the cluster will become unavailable. This is a big problem for a production Hadoop cluster. In this recipe, we list the steps to configure NameNode HA.
In order for the standby NameNode to automatically recover from the active NameNode failure, the NameNode HA implementation requires that the edit logs of the standby NameNode to be always kept synchronized with the active NameNode. Hadoop HA offers two ways to do this. One is based on Quorum and the other is based on shared storage using NFS. In this recipe, we will only show you how to configure HA using Quorum.