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https://issues.apache.org/jira/browse/MAPREDUCE-1333?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12800121#action_12800121
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Zhaoning Zhang commented on MAPREDUCE-1333:
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virtual machines in the XenServer cluster, some nodes are allocated with 1 cpu
and some nodes with 2 or 3.
but I think it's a inter-dependence structure problem, the reduce will always
waiting for the maps to finish its tasks, why not let the maps to use full
resources separately?
> Parallel running tasks on one single node may slow down the performance
> -----------------------------------------------------------------------
>
> Key: MAPREDUCE-1333
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-1333
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: jobtracker, task, tasktracker
> Affects Versions: 0.20.1
> Reporter: Zhaoning Zhang
>
> When I analysis running tasks performance, I found that parallel running
> tasks on one single node will not be better performance than the serialized
> ones.
> We can set mapred.tasktracker.{map|reduce}.tasks.maximum = 1 individually,
> but there will be parallel map AND reduce tasks.
> And I wonder it's true in the real commercial clusters?
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