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HDFS Forum

NameNode functions

  • #34199
    Swapnil Patil

    Does namenode writes anything on datanode? I am confused in the following things..
    1) If I have set up replication factor to 3..then does namenode writes these replicas to 3 datanodes? or 1 datanode writes to other datanodes?

    Thanks inadvance

  • Author
  • #34235
    Ravi Kiran

    Hi Swapnil,
    The namenode never , ever writes blocks to a datanode directly. The data nodes form a pipeline and the first one sends the block to the second and so on downstream.
    You can see the process of a FileWrite from here

    Ravi Magham

    Swapnil Patil

    Hi Ravi,
    Thanks for your reply..
    How one datanode recognizes other datanodes in the cluster? I mean which file they refer to for other datanodes IP addresses?
    Do they refer etc/hosts file or slaves file
    What kind of setings I need to do in the respective datanode config files.

    Robert Molina

    Hi Swapnil,
    Have you tried just installing the cluster with Ambari? It makes it easier to set up the cluster and administer.


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