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  1. Hadoop HDFS
  2. HDFS-11833

HDFS architecture documentation describes outdated placement policy

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    • Hadoop Flags:
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      Description

      Hello

      I've noticed inconsistencies in the default block placement policy between what one can read on several websites and what is stated in the official documentation.

      After digging, I've found out that the proper default placement policy is :

       * The replica placement strategy is that if the writer is on a datanode,
       * the 1st replica is placed on the local machine, 
       * otherwise a random datanode. The 2nd replica is placed on a datanode
       * that is on a different rack. The 3rd replica is placed on a datanode
       * which is on a different node of the rack as the second replica.
       

      source

      HADOOP-5734 has been opened regarding this mistake several years ago and has eventually been merged but unfortunately this fix has been overwritten by Alejandro Abdelnur in SVN commit.

      dud

        Attachments

        1. HADOOP-14411.001.patch
          3 kB
          Chen Liang
        2. HADOOP-14411.002.patch
          3 kB
          Chen Liang

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            • Assignee:
              vagarychen Chen Liang
              Reporter:
              dud dud
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                Updated:
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