2014-08-30 QJM (HDFS High Availability Using the Quorum Journal Manager) Hadoop Issue of Old Namenode Namenode is SPOF(Single Point of Failure) Purpose of Namenode HighAvaliability Easy Sync Active/ Slave Easy Deployment No SPOF Hadoop Cluster Economically What is Namenode HA? By Apache Hadoop2.0 Included CDH4.1