In the Hadoop Distributed File System (HDFS), there are primarily two types of nodes that handle data storage and management: the NameNode and the DataNode. Understanding their roles is crucial to grasping how Hadoop works.

Understanding Hadoop Nodes: NameNode and DataNode

Let's break down the functions of each node:

• NameNode: This is the central component of HDFS. It acts as the master server. It manages the file system namespace, meaning it keeps track of the file structure (directories and files) and the metadata for all files. Crucially, it knows where each file is stored across the cluster, but it doesn't store the actual file data itself. Think of it as the librarian who knows where every book (data block) is located in the library (cluster) but doesn't hold the books themselves.
• DataNode: These nodes are the workhorses of HDFS. They store the actual data blocks that make up files. DataNodes are responsible for serving read and write requests from clients and performing block creation, deletion, and replication as instructed by the NameNode. They report their block information periodically to the NameNode. These are the shelves in the library that hold the books (data blocks).

Relating to Master and Worker Nodes

Based on their roles:

• The NameNode directs operations, manages the metadata, and coordinates activities across the cluster. This fits the description of a Master Node.
• The DataNodes store and serve the data blocks, performing the actual storage work under the direction of the NameNode. This fits the description of Worker Nodes.

Therefore, in Hadoop, the DataNode is the Worker Node and the NameNode is the Master Node.

Analyzing the Given Options

Let's look at the options provided:

• Option 1: Worker Node and Master Node respectively. This means DataNode is the Worker Node and NameNode is the Master Node. This aligns with our understanding.
• Option 2: Master Node and Worker Node respectively. This means DataNode is the Master Node and NameNode is the Worker Node. This is incorrect as the NameNode is the master.
• Option 3: Both Worker Nodes. This is incorrect as NameNode is the master.
• Option 4: Both Master Nodes. This is incorrect as DataNodes are the workers.

Based on the analysis, Option 1 correctly identifies the roles of the DataNode and NameNode.

Revision Table: Hadoop Nodes

Additional Information on HDFS Architecture

HDFS is designed with a single NameNode (though high availability configurations exist) and multiple DataNodes. This architecture provides high throughput for data access and is highly scalable. The separation of metadata (managed by NameNode) and actual data storage (managed by DataNodes) is a key design principle. Data replication across multiple DataNodes ensures fault tolerance; if one DataNode fails, the data can still be accessed from another DataNode holding a replica.