What is DataNode and name Node?

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.

What is a NameNode in Hadoop?

The NameNode is the centerpiece of an HDFS file system. It keeps the directory tree of all files in the file system, and tracks where across the cluster the file data is kept. The NameNode is a Single Point of Failure for the HDFS Cluster. When the NameNode goes down, the file system goes offline.

How does Hadoop work when a DataNode fails?

As soon as the data node is declared dead/non-functional all the data blocks it hosts are transferred to the other data nodes with which the blocks are replicated initially. This is how Namenode handles datanode failures. HDFS works in Master/Slave mode where NameNode act as a Master and DataNodes act as a Slave.

Which file contains the NameNode and Datanode information?

hdfs-site.xml file
The hdfs-site. xml file contains information such as the value of replication data, namenode path, and datanode paths of your local file systems.

What are name nodes?

The NameNode is the centerpiece of an HDFS file system. It keeps the directory tree of all files in the file system, and tracks where across the cluster the file data is kept. The NameNode responds the successful requests by returning a list of relevant DataNode servers where the data lives.

What is purpose of NameNode?

The NameNode is the centerpiece of an HDFS file system. It keeps the directory tree of all files in the file system, and tracks where across the cluster the file data is kept.

What happens when Datanode goes down?

Basic Operations of Datanode: When one of Datanode gets down then it will not make any effect on Hadoop cluster due to replication. All Datanodes are synchronized in the Hadoop cluster in a way that they can communicate with each other for various operations.

What happens failing Datanode?

DFSClient will iterate over that list of Datanodes and write the block A in those locations. If block write fails in the first datanodes, it’ll abandon the block write and ask namenode a new set of datanodes where it can attempt to write again.

How do I start DFS?

Installing DFS Namespaces

1. Open Server Manager, click Manage, and then click Add Roles and Features.
2. On the Server Selection page, select the server or virtual hard disk (VHD) of an offline virtual machine on which you want to install DFS.
3. Select the role services and features that you want to install.