Question: What Is The Difference Between NameNode And DataNode In Hadoop?

What are three features of Hadoop?

Features of HadoopHadoop is Open Source.

Hadoop cluster is Highly Scalable.

Hadoop provides Fault Tolerance.

Hadoop provides High Availability.

Hadoop is very Cost-Effective.

Hadoop is Faster in Data Processing.

Hadoop is based on Data Locality concept.

Hadoop provides Feasibility.More items….

What is DataNode and NameNode in Hadoop?

The NameNode keeps an image of the entire file system namespace and file Blockmap in memory. … The DataNode stores HDFS data in files in its local file system. The DataNode has no knowledge about HDFS files. It stores each block of HDFS data in a separate file in its local file system.

What is the difference between a NameNode and a secondary NameNode?

Secondary namenode is just a helper for Namenode. It gets the edit logs from the namenode in regular intervals and applies to fsimage. Once it has new fsimage, it copies back to namenode. Namenode will use this fsimage for the next restart, which will reduce the startup time.

What is a Datanode in Hadoop?

DataNodes store data in a Hadoop cluster and is the name of the daemon that manages the data. File data is replicated on multiple DataNodes for reliability and so that localized computation can be executed near the data. Within a cluster, DataNodes should be uniform.

What is Hadoop architecture?

The Hadoop architecture is a package of the file system, MapReduce engine and the HDFS (Hadoop Distributed File System). The MapReduce engine can be MapReduce/MR1 or YARN/MR2. A Hadoop cluster consists of a single master and multiple slave nodes.

What happens if NameNode crashes in Hadoop?

If NameNode gets fail the whole Hadoop cluster will not work. Actually, there will not any data loss only the cluster work will be shut down, because NameNode is only the point of contact to all DataNodes and if the NameNode fails all communication will stop.

What are the main files of Hadoop NameNode?

What are the configuration files in Hadoop? HADOOP-ENV.sh->>It specifies the environment variables that affect the JDK used by Hadoop Daemon (bin/hadoop). … CORE-SITE. … HDFS-SITE. … MAPRED-SITE. … Masters->>It is used to determine the master Nodes in Hadoop cluster. … Slave->>It is used to determine the slave Nodes in Hadoop cluster.Sep 20, 2018

When the primary name node goes down its place is taken up by?

4. ________ NameNode is used when the Primary NameNode goes down. Explanation: Secondary namenode is used for all time availability and reliability.

What is DataNode?

DataNode: DataNodes are the slave nodes in HDFS. Unlike NameNode, DataNode is a commodity hardware, that is, a non-expensive system which is not of high quality or high-availability. The DataNode is a block server that stores the data in the local file ext3 or ext4.

What is InputSplit in Hadoop?

InputSplit in Hadoop MapReduce is the logical representation of data. It describes a unit of work that contains a single map task in a MapReduce program. Hadoop InputSplit represents the data which is processed by an individual Mapper. The split is divided into records.

What are the two components of Hadoop?

Components of HadoopHadoop HDFS – Hadoop Distributed File System (HDFS) is the storage unit of Hadoop.Hadoop MapReduce – Hadoop MapReduce is the processing unit of Hadoop.Hadoop YARN – Hadoop YARN is a resource management unit of Hadoop.Mar 1, 2021

How a NameNode and DataNode communicate with each other?

All communication between Namenode and Datanode is initiated by the Datanode, and responded to by the Namenode….4.4 NameNode <-> DataNodeDataNode sends heartbeat. The DataNode sends a heartbeat message every few seconds. … DataNode sends block report. … DataNode notifies BlockReceived.

Is Hadoop a database?

Hadoop is not a type of database, but rather a software ecosystem that allows for massively parallel computing. It is an enabler of certain types NoSQL distributed databases (such as HBase), which can allow for data to be spread across thousands of servers with little reduction in performance.

How does Hadoop distributed file system work?

How does HDFS work? With the Hadoop Distributed File system the data is written once on the server and subsequently read and re-used many times thereafter. … The NameNode also manages access to the files, including reads, writes, creates, deletes and replication of data blocks across different data nodes.

What is Hadoop and its advantages?

Hadoop is a highly scalable storage platform because it can store and distribute very large data sets across hundreds of inexpensive servers that operate in parallel. Unlike traditional relational database systems (RDBMS) that can’t scale to process large amounts of data.

What is the use of secondary NameNode?

The secondary NameNode merges the fsimage and the edits log files periodically and keeps edits log size within a limit. It is usually run on a different machine than the primary NameNode since its memory requirements are on the same order as the primary NameNode.

What happens if secondary NameNode fails?

If NameNode is failed, File System metadata can be recovered from the last saved FsImage on the Secondary NameNode but Secondary NameNode can’t take the primary NameNode’s functionality.

What is the 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. It does not store the data of these files itself.

What is MapReduce in Hadoop?

Hadoop MapReduce is a software framework for easily writing applications which process vast amounts of data (multi-terabyte data-sets) in-parallel on large clusters (thousands of nodes) of commodity hardware in a reliable, fault-tolerant manner.

Which machine is NameNode?

Here is a recommended setup from the Hadoop setup guide. Typically one machine in the cluster is designated as the NameNode and another machine the as JobTracker, exclusively. These are the masters. The rest of the machines in the cluster act as both DataNode and TaskTracker.

What is Fsimage in Hadoop?

The entire file system namespace, including the mapping of blocks to files and file system properties, is stored in a file called the FsImage. The FsImage is stored as a file in the NameNode’s local file system too. The NameNode keeps an image of the entire file system namespace and file Blockmap in memory.