Following are some important points to remember about the HDFS HA using the QJM architecture:
- In the cluster, there are two separate machines—the active state NameNode and standby state NameNode.
- At any point in time, exactly one of the NameNodes is in an active state, and the other is in a standby state.
- The active NameNode manages the requests from all client DataNodes in the cluster, while the standby remains a slave.
- All the DataNodes are configured in such a way that they send their block reports and heartbeats to both active and standby NameNodes.
- Both NameNodes, active and standby, remain synchronized with each other by communicating with a group of separate daemons called JournalNodes (JNs).
- When a client ...
