August 2017
Beginner to intermediate
284 pages
6h 51m
English
Content preview from Mastering Apache Storm
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Namenode
The namenode is the master node in an HDFS cluster. It is responsible for managing the filesystem metadata and operations. It does not store any user data--but only the filesystem tree of all files in the cluster. It also keeps track of the physical locations of the blocks that are part of the files.
Since, the namenode keeps all the data in RAM, it should be deployed on a machine with a large amount of RAM. Also, no other processes should be hosted on the machine that is hosting the namenode so that all the resources are dedicated to it.
The namenode is the single point of failure in an HDFS cluster. If the namenode dies, no operations can take place on an HDFS cluster.
Figure 1: HDFS Cluster
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