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https://issues.apache.org/jira/browse/MAPREDUCE-2636?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13546326#comment-13546326
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Eli Collins commented on MAPREDUCE-2636:
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Btw as of HDFS-3672 the disk location information is exposed.
> Scheduling over disks horizontally
> ----------------------------------
>
> Key: MAPREDUCE-2636
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-2636
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: job submission
> Reporter: Evert Lammerts
> Priority: Minor
>
> Based on this message:
> http://mail-archives.apache.org/mod_mbox/hadoop-hdfs-user/201106.mbox/browser
> The JT schedules tasks on nodes based on metadata it gets from the NN. The
> namenode does not know on which disk a block resides. It might happen that on
> a node running 4 tasks, all read from the same disk. This can affect
> performance.
> An optimization might be to schedule horizontally over disks instead of
> nodes. Any ideas?
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