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From "Raghu Angadi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4396) sort on 400 nodes is now slower than in 18
Date Fri, 17 Oct 2008 18:01:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4396?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12640600#action_12640600
] 

Raghu Angadi commented on HADOOP-4396:
--------------------------------------

I think this highlights some issues that are worth considering for improvement.

It looks as though some mapper that gets slightly behind will end up getting disproportionately
hard.. slowing the progress much worse than one would expect. And it does not even need to
be any hardware degredation. This kind of bad feedback gets only worse as the cluster size
increases.

> sort on 400 nodes is now slower than in 18
> ------------------------------------------
>
>                 Key: HADOOP-4396
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4396
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.19.0
>            Reporter: Jothi Padmanabhan
>            Assignee: Jothi Padmanabhan
>            Priority: Blocker
>             Fix For: 0.19.0
>
>         Attachments: 4396-v3.patch
>
>
> Sort on 400 nodes on  hadoop release 18 takes about 29 minutes, but with the 19 branch
takes about 32 minutes. This behavior is consistent.

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