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Date: Fri, 18 Jun 2010 01:45:24 -0400 (EDT)
From: "Hadoop QA (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
Subject: [jira] Commented: (MAPREDUCE-1831) Delete the co-located replicas
 when raiding file
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    [ https://issues.apache.org/jira/browse/MAPREDUCE-1831?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12880073#action_12880073 ] 

Hadoop QA commented on MAPREDUCE-1831:
--------------------------------------

-1 overall.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12446833/MAPREDUCE-1831.20100610.txt
  against trunk revision 955543.

    +1 @author.  The patch does not contain any @author tags.

    +1 tests included.  The patch appears to include 2 new or modified tests.

    +1 javadoc.  The javadoc tool did not generate any warning messages.

    +1 javac.  The applied patch does not increase the total number of javac compiler warnings.

    +1 findbugs.  The patch does not introduce any new Findbugs warnings.

    +1 release audit.  The applied patch does not increase the total number of release audit warnings.

    +1 core tests.  The patch passed core unit tests.

    -1 contrib tests.  The patch failed contrib unit tests.

Test results: http://hudson.zones.apache.org/hudson/job/Mapreduce-Patch-h4.grid.sp2.yahoo.net/252/testReport/
Findbugs warnings: http://hudson.zones.apache.org/hudson/job/Mapreduce-Patch-h4.grid.sp2.yahoo.net/252/artifact/trunk/build/test/findbugs/newPatchFindbugsWarnings.html
Checkstyle results: http://hudson.zones.apache.org/hudson/job/Mapreduce-Patch-h4.grid.sp2.yahoo.net/252/artifact/trunk/build/test/checkstyle-errors.html
Console output: http://hudson.zones.apache.org/hudson/job/Mapreduce-Patch-h4.grid.sp2.yahoo.net/252/console

This message is automatically generated.

> Delete the co-located replicas when raiding file
> ------------------------------------------------
>
>                 Key: MAPREDUCE-1831
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1831
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: contrib/raid
>    Affects Versions: 0.22.0
>            Reporter: Scott Chen
>            Assignee: Scott Chen
>             Fix For: 0.22.0
>
>         Attachments: MAPREDUCE-1831.20100610.txt, MAPREDUCE-1831.txt, MAPREDUCE-1831.v1.1.txt
>
>
> In raid, it is good to have the blocks on the same stripe located on different machine.
> This way when one machine is down, it does not broke two blocks on the stripe.
> By doing this, we can decrease the block error probability in raid from O(p^3) to O(p^4) which can be a hugh improvement (where p is the replica missing probability).
> One way to do this is that we can add a new BlockPlacementPolicy which deletes the replicas that are co-located.
> So when raiding the file, we can make the remaining replicas live on different machines.

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