Question - Can you recover a NameNode when it is down? If so, how?
Answer -
Yes, it is possible to recover a NameNode when it is down. Here’s how you can do it:
- Use the FsImage (the file system metadata replica) to launch a new NameNode.
- Configure DataNodes along with the clients so that they can acknowledge and refer to newly started NameNode.
- When the newly created NameNode completes loading the last checkpoint of the FsImage (that has now received enough block reports from the DataNodes) loading process, it will be ready to start serving the client.
However, the recovery process of a NameNode is feasible only for smaller clusters. For large Hadoop clusters, the recovery process usually consumes a substantial amount of time, thereby making it quite a challenging task.