Scalability of the NameNode has been a key issue for HDFS clusters. Because the entire file system metadata is stored in memory on a single NameNode, and all metadata operations are processed on this single system, the NameNode both limits the growth in size of the cluster and makes the NameService a bottleneck for the MapReduce framework as demand increases. HDFS Federation horizontally scales the NameService using multiple federated NameNodes/namespaces. The federated NameNodes share the DataNodes in the cluster as a common storage layer. HDFS Federation also adds client-side namespaces to provide a unified view of the file system. In this talk, Hortonworks co-founder and key architect, Suresh Srinivas will discuss the benefits, features and best practices for implementing HDFS Federation.