What is the Difference Between NameNode and DataNode in Hadoop

The main difference between NameNode and DataNode in Hadoop is that the NameNode is the master node in Hadoop Distributed File System that manages the file system metadata while the DataNode is a slave node in Hadoop distributed file system that stores the actual data as instructed by the NameNode.

Hadoop is an open source framework developed by Apache Software Foundation. It allows storing and processing a large amount of data simultaneously across clusters of computers in a distributed environment. HDFS, on the other hand, is the distributed file system of Hadoop, which distributes data over multiple machines and replicates them to increase durability, reliability, and availability. Moreover, HDFS works according to master-slave architecture. Namenode and dataNode are components of this architecture.

Key Areas Covered

1. What is NameNode
     – Definition, Functionality
2. What is DataNode
     – Definition, Functionality
3. What is the Relationship Between NameNode and DataNode
     – Outline of Association
4. What is the Difference Between NameNode and DataNode in Hadoop
     – Comparison of Key Differences

Key Terms

DataNode, Hadoop, HDFS, NameNode

What is NameNode

Metadata refers to a small amount of data, and it requires a minimum amount of memory to store. Namenode stores this metadata of all the files in HDFS. Metadata includes file permission, names, and location of each block. A block is a minimum amount of data that can be read or write. Moreover, NameNode maps these blocks to dataNodes. Furthermore, nameNode manages all other dataNodes. Master node is an alternative name for nameNode.

What is DataNode

The nodes other than the nameNode are called dataNodes. Slave node is another name for dataNode. The data nodes store and retrieve blocks as instructed by the nameNode.

All dataNodes continuously communicate with the name node. They also inform the nameNode about the blocks they are storing. Furthermore, the dataNodes also perform block creation, deletion,  and replication as instructed by the nameNode.

Relationship Between NameNode and DataNode

• Namenode and Datanode operate according to master-slave architecture in Hadoop Distributed File System (HDFS).

Difference Between NameNode and DataNode

Definition

NameNode is the controller and manager of HDFS whereas DataNode is a node other than the NameNode in HDFS that is controlled by the NameNode. Thus, this is the main difference between NameNode and DataNode in Hadoop.

Synonyms

Moreover, Master node is another name for NameNode while Slave node is another name for DataNode.

Main Functionality

While nameNode handles the metadata of all the files in HDFS and controls the dataNodes, Datanode store and retrieve blocks according to the master node’s instructions. Hence, this is another difference between NameNode and DataNode in Hadoop.

Conclusion

The main difference between NameNode and DataNode in Hadoop is that the NameNode is the master node in HDFS that manages the file system metadata while the DataNode is a slave node in HDFS that stores the actual data as instructed by the NameNode. In brief, NameNode controls and manages a single or multiple data nodes.

Reference:

1. “HDFS – Javatpoint.” Www.javatpoint.com, Available here.

Image Courtesy:

1. “Hdfsarchitecture” By Magnai17 – Own work (CC BY-SA 4.0) via Commons Wikimedia