1.

Explain the Storage Unit In Hadoop (HDFS).

Answer»

HDFS is the Hadoop Distributed File System, is the storage layer for Hadoop. The files in HDFS are SPLIT into BLOCK-size PARTS called data blocks. These blocks are saved on the slave nodes in the cluster. By default, the size of the block is 128 MB by default, which can be configured as per our necessities. It follows the master-slave architecture. It contains two daemons- DataNodes and NameNode.

NameNode
The NameNode is the master daemon that operates on the master node. It saves the filesystem metadata, that is, files names, data about blocks of a file, blocks locations, PERMISSIONS, etc. It manages the Datanodes.
DataNode
The DataNodes are the slave daemon that operates on the slave nodes. It saves the actual BUSINESS data. It serves the client read/write requests based on the NameNode instructions. It stores the blocks of the files, and NameNode stores the metadata like block locations, permission, etc.


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