Namenode vs. Backup node vs. Checkpoint Namenode

• NameNode
• manages the metadata i.e. info about all the files present in the HDFS on a hadoop cluster
• uses 2 files for the namespace :
• FS image : keeps track of the latest checkpoint of the namespace
• edit logs : A log of changes that have been made to the namespace since checkpoint.

• Checkpoint Node
• Same structure as Namenode
• creates checkpoints for the namespace at regular intervals by downloading the edits and fsimage file from the NameNode and merging it
• keeps track of the latest checkpoint

• Backup node
• Also provides checkpoint functionality as the Checkpoint node
• Additionally, maintains up-to-date in-memory copy of the file system namespace that is in sync with the active NameNode.