4. Operating a NameNode HA cluster

  • While operating an HA cluster, the Active NameNode cannot commit a transaction if it cannot write successfully to a quorum of the JournalNodes.

  • When restarting an HA cluster, the steps for initializing JournalNodes and NN2 can be skipped.

  • Start the services in the following order:

    1. JournalNodes

    2. NameNodes


      Verify that the ZKFailoverController (ZKFC) process on each node is running so that one of the NameNodes can be converted to active state.

    3. DataNodes

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