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Posted to common-dev@hadoop.apache.org by "Doug Cutting (JIRA)" <ji...@apache.org> on 2008/05/26 19:52:01 UTC

[jira] Commented: (HADOOP-3443) map outputs should not be renamed between partitions

    [ https://issues.apache.org/jira/browse/HADOOP-3443?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12599886#action_12599886 ] 

Doug Cutting commented on HADOOP-3443:
--------------------------------------

> Should this be fixed in 0.17? 

Is it a regression?


> map outputs should not be renamed between partitions
> ----------------------------------------------------
>
>                 Key: HADOOP-3443
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3443
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.17.0
>            Reporter: Owen O'Malley
>            Assignee: Owen O'Malley
>            Priority: Critical
>         Attachments: hadoop-3443-1.patch
>
>
> If a map finishes with out having to spill its data buffer, the map outputs are sorted and written to disk. However, no care is taken to make sure that the same partition is used to write it out before it is renamed. On nodes with multiple disks assigned to the task trackers, this will likely cause an addition read/write cycle to disk that is very expensive.

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