DATABASE FUNDAMENTALS
BASICS OF BIG DATA
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Size of the file requested
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Block ID of the file requested
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Block ID and hostname of any one of the data nodes containing that block
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Block ID and hostname of all the data nodes containing that block
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Detailed explanation-1: -When the local file accumulates data worth over one HDFS block size, the client contacts the NameNode. The NameNode inserts the file name into the file system hierarchy and allocates a data block for it. The NameNode responds to the client request with the identity of the DataNode and the destination data block.
Detailed explanation-2: -The protocol used for communication between NameNode and DataNodes is RPC, and the protocol used for data transfer is HDFS over HTTP.
Detailed explanation-3: -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.
Detailed explanation-4: -Your answer Client applications talk to the NameNode whenever they wish to locate a file, or when they want to add/copy/move/delete a file on HDFS. The NameNode responds the successful requests by returning a list of relevant DataNode servers where the data lives.