Home Forums HDFS NameNode functions

This topic contains 3 replies, has 3 voices, and was last updated by  Robert Molina 11 months, 3 weeks ago.

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  • #34199

    Swapnil Patil
    Participant

    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

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  • #39179

    Robert Molina
    Moderator

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

    Regards,
    Robert

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    #34341

    Swapnil Patil
    Participant

    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.

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    #34235

    Ravi Kiran
    Member

    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

    http://books.google.co.in/books?id=drbI_aro20oC&pg=PA70&lpg=PA70&dq=anatomy+of+file+write+in+hadoop&source=bl&ots=tZDmtaj0d8&sig=Sl6aT4XVhHuXYxN_De7teMQoEu8&hl=en&sa=X&ei=RUMnUoSvE4_yiQKiy4C4Cg&ved=0CDwQ6AEwAw#v=onepage&q=anatomy%20of%20file%20write%20in%20hadoop&f=false

    Regards
    Ravi Magham

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