Solution

The correct answer is option 1

Key Points

The main difference between NameNode and DataNode in Hadoop is that the NameNode is the master node in Hadoop Distributed File System (HDFS) 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.

Additional Information

• NameNode stores the metadata of all files in HDFS. Metadata includes file permission, names, and location of each block. Namenode maps these blocks to DataNodes.
• The data nodes store and retrieve blocks as instructed by the NameNode.