CheckPoint Node

In this chapter

This chapter explains checkpoint node and how to configure a checkpoint node to create checkpoints of namespace periodically.

Introduction

NameNode persists its namespace using two files: fsimage, which is the latest checkpoint of the namespace and edits, a journal (log) of changes to the namespace since the checkpoint. When a NameNode starts up, it merges the fsimage and edits journal to provide an up-to-date view of the file system meta-data. The NameNode then overwrites fsimage with the new HDFS state and begins a new edits journal.

The Checkpoint node periodically creates checkpoints of the namespace. It downloads fsimage and edits from the active NameNode, merges them locally, and uploads the new image back to the active NameNode. The Checkpoint node usually runs on a different machine than the NameNode since its memory requirements are on the same order as the NameNode.

The Checkpoint node stores the latest checkpoint in a directory that is structured the same as the NameNode's directory. This allows the check-pointed image to be always available for reading by the NameNode if necessary.

Multiple CheckPoint nodes may be configured on the cluster.

To configure CheckPoint nodes or perform start/stop operations on them, navigate to CheckPoint Node tab.

name_node

Adding CheckPoint Nodes

To add checkpoint nodes to your cluster, follow the guidelines mentioned below

Configuring CheckPoint Nodes

To configure existing CheckPoint nodes, follow the guidelines mentioned below

name_node

Start/Stop CheckPoint Nodes

To start/stop existing CheckPoint nodes, follow the guidelines mentioned below



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