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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3443) map outputs should not be renamed between partitions
Date Mon, 26 May 2008 17:52:01 GMT

    [ 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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