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From "Mingliang Liu (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-10335) Mover$Processor#chooseTarget() always chooses the first matching target datanode
Date Wed, 27 Apr 2016 02:13:12 GMT
Mingliang Liu created HDFS-10335:
------------------------------------

             Summary: Mover$Processor#chooseTarget() always chooses the first matching target
datanode
                 Key: HDFS-10335
                 URL: https://issues.apache.org/jira/browse/HDFS-10335
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: balancer & mover
    Affects Versions: 2.8.0
            Reporter: Mingliang Liu
            Assignee: Mingliang Liu
            Priority: Critical


Currently the {{org.apache.hadoop.hdfs.server.mover.Mover$Processor#chooseTarget()}} always
chooses the first matching target datanode from the candidate list. This may make the mover
schedule a lot of task to a few of the datanodes (first several datanodes of the candidate
list). The overall performance will suffer significantly from this because of the saturated
network/disk usage. Specially, if the {{dfs.datanode.balance.max.concurrent.moves}} is set,
the scheduled move task will be queued on a few of the datanodes, regardless of other available
storage resources. We need an algorithm which can distribute the move tasks approximately
even across all the candidate target datanodes (storages).

Thanks [~szetszwo] for offline discussion.



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