Hadoop includes three main Components

• HDFS
• MapReduce
• YARN

HDFS:

• HDFS means Hadoop Distributed File System and it manages big data sets with high volume.
• HDFS stores the data at distributed manner and it is the primary storage system
• HDFS allows read and write the files but cannot updated the files in HDFS.
• When we move file in HDFS that file are automatically split into small files and that small files are replicated of three different servers.
• HDFS are implemented by Master Slave architecture.Master means namenode and Slave means datande.

Components of HDFS:

NameNode:

• NameNode is the heart and master oh Hadoop
• It maintains the namespace system of hadoop
• NameNode stores the metadata of data blocks that data are permanently stored on Local disk
• It reduced disk space also.
• There are two types of NameNode(active and standby)

Secondary Node:

• Main role of secondary namenode is copy and merge the namespace.
• Secondary namenode requires huge amount of memory to merge the files.
• If namenode failure namespace images are stored in secondary namenode and it can be restart the namenode.

DataNode:

• DataNode also known as slaves.
• It can be used to actual storage.
• Work of Datanode are based on NameNode instructions only

MapReduce:

• MapReduce is the software framework and it is used to process large amount of data in Parallel.
• There are two tasks in MapReduce.(Click Here to know more details about Map Reduce)

1.Mapper Task:

• It takes the one input and divide into small parts and distribute to another node.
• To solve all small programs and send the results to master node.

2.Reducer Task:

• It combines the all master node results and arranging the results at some formats.

YARN:

• YARN means Yet Another Resource Negotiator.
• YARN is the resource management responsible for managing resources in cluster and scheduling applications.
• It also Known as MapReduce2
• Responsible of YARN is managing and monitoring the work loads.
• Yarn Having following two components

               1.Resource Manager(NameNode)

               2.Node Manager(DataNode)

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