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https://issues.apache.org/jira/browse/HDFS-10335?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15260873#comment-15260873
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Hadoop QA commented on HDFS-10335:
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|| Subsystem || Report/Notes ||
| JIRA Patch URL | 
https://issues.apache.org/jira/secure/attachment/12800935/HDFS-10335.000.patch |
| JIRA Issue | HDFS-10335 |
| Console output | 
https://builds.apache.org/job/PreCommit-HDFS-Build/15309/console |
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> Mover$Processor#chooseTarget() always chooses the first matching target 
> storage group
> -------------------------------------------------------------------------------------
>
>                 Key: HDFS-10335
>                 URL: https://issues.apache.org/jira/browse/HDFS-10335
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: balancer & mover
>    Affects Versions: 2.8.0
>            Reporter: Mingliang Liu
>            Assignee: Mingliang Liu
>            Priority: Critical
>         Attachments: HDFS-10335.000.patch
>
>
> Currently the 
> {{org.apache.hadoop.hdfs.server.mover.Mover$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 storage group, regardless 
> of other available storage groups. We need an algorithm which can distribute 
> the move tasks approximately even across all the candidate target storage 
> groups.
> Thanks [~szetszwo] for offline discussion.



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