What is Rack Awareness in HDFS?

1.	What is Rack Awareness in HDFS?
Answer» In Hadoop, Rack awareness is the concept of choosing the DataNodes which are closer according to the rack information. By default, Hadoop ASSUMES that all the nodes belong to the same rack. In order to improve the network TRAFFIC while reading/writing HDFS files that are on the same or a NEARBY rack, NameNode USES the DataNode to read/ write requests. To achieve rack information, the rack ids of each DataNode are MAINTAINED by HDFS NameNode. This concept in HDFS is known as Rack Awareness.

Answer»

In Hadoop, Rack awareness is the concept of choosing the DataNodes which are closer according to the rack information. By default, Hadoop ASSUMES that all the nodes belong to the same rack.

In order to improve the network TRAFFIC while reading/writing HDFS files that are on the same or a NEARBY rack, NameNode USES the DataNode to read/ write requests. To achieve rack information, the rack ids of each DataNode are MAINTAINED by HDFS NameNode. This concept in HDFS is known as Rack Awareness.

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