In HA there will be two Namenodes, one is Active and other one is in the Standby state.The Active Namenode is primarily responsible for all running, upcoming operations and client requests in the cluster. At same time Standby acts as a slave.To maintain synchronization between Active and Standby nodes they both communicate with a group of demons called JournalNodes(JNs). If there any Namespace modifications done by Active name node logs a modification record to a majority of these present JNs.The standby node reads the edits from the JNs and continuously watches the changes in edit log from JNs. Standby node updates its own namespace of observes in edits every time.JNs are shared edits in presence of QJM.when failover happens, the Standby ensures that it has read all edits from JNs before it takes over the Active position. Standby acts as secondary name node because it performs all tasks done by secondary name node. So in HA configuration cluster no need of Secondary Namenode. Hope this helps you. @karthik nedunchezhiyan
... View more
