Table of Contents
What Is the Role of the NameNode in Hadoop Distributed File System?
Understand the critical role of the NameNode in HDFS for your Big Data certification. Learn how this master server maintains file system metadata and manages block locations without storing actual data or executing jobs.
Question
What is the role of the NameNode in HDFS?
A. To replicate data across clusters
B. To store actual data blocks
C. To maintain metadata and manage block locations
D. To execute MapReduce jobs directly
Answer
C. To maintain metadata and manage block locations
Explanation
In the Hadoop Distributed File System (HDFS), the NameNode acts as the master server and central arbitrator. Its primary role is to maintain the entire file system namespace (metadata) and manage where data blocks are located across the cluster. This metadata includes directory structures, file permissions, replication factors, and the mapping of which specific DataNodes hold which blocks of a file. The NameNode does not store the actual data blocks, replicate data (DataNodes handle this based on NameNode instructions), or execute MapReduce jobs (which is managed by YARN and executed on worker nodes).