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https://issues.apache.org/jira/browse/HADOOP-5603?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12694303#action_12694303
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Hairong Kuang commented on HADOOP-5603:
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I did an experiment in a dfs cluster with 3150 node. The cluster is full with
no space to place any block. The trunk takes around 6.5s to declare failure in
an effort to place a block to 2 nodes. With the patch, it takes around 2.1s to
declare failure.
> Improve block placement performance
> -----------------------------------
>
> Key: HADOOP-5603
> URL: https://issues.apache.org/jira/browse/HADOOP-5603
> Project: Hadoop Core
> Issue Type: Improvement
> Components: dfs
> Reporter: Hairong Kuang
> Assignee: Hairong Kuang
> Fix For: 0.21.0
>
> Attachments: blockPlace.patch
>
>
> ReplicationTargetChooser chooses targets by iteratively selecting random
> nodes first and then filtering good targets until the required number of
> targets are chosen. This code may require selecting random nodes multiple
> times, thus introducing multiple traversals of the given portion of the
> cluster map. This code can be improved by traversing the portion of the
> cluster map only once.
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