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Date: Fri, 5 Nov 2010 01:50:46 -0400 (EDT)
From: "Hadoop QA (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
Subject: [jira] Commented: (MAPREDUCE-1861) Raid should rearrange the
 replicas while raiding
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    [ https://issues.apache.org/jira/browse/MAPREDUCE-1861?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12928486#action_12928486 ] 

Hadoop QA commented on MAPREDUCE-1861:
--------------------------------------

-1 overall.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12449371/MAPREDUCE-1861.txt
  against trunk revision 963986.

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

    +1 tests included.  The patch appears to include 3 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 failed core unit tests.

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

Test results: http://hudson.zones.apache.org/hudson/job/Mapreduce-Patch-h6.grid.sp2.yahoo.net/598/testReport/
Findbugs warnings: http://hudson.zones.apache.org/hudson/job/Mapreduce-Patch-h6.grid.sp2.yahoo.net/598/artifact/trunk/build/test/findbugs/newPatchFindbugsWarnings.html
Checkstyle results: http://hudson.zones.apache.org/hudson/job/Mapreduce-Patch-h6.grid.sp2.yahoo.net/598/artifact/trunk/build/test/checkstyle-errors.html
Console output: http://hudson.zones.apache.org/hudson/job/Mapreduce-Patch-h6.grid.sp2.yahoo.net/598/console

This message is automatically generated.

> Raid should rearrange the replicas while raiding
> ------------------------------------------------
>
>                 Key: MAPREDUCE-1861
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1861
>             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-1861.txt, MAPREDUCE-1861.txt
>
>
> Raided file introduce extra dependencies on the blocks on the same stripe.
> Therefore we need a new way to place the blocks.
> It is desirable that raided file satisfies the following two conditions:
> a. Replicas on the same stripe should be on different machines (or racks)
> b. Replicas of the same block should be on different racks
> MAPREDUCE-1831 will try to delete the replicas on the same stripe and the same machine (a).
> But in the mean time, it will try to maintain the number of distinct racks of one block (b).
> We cannot satisfy (a) and (b) at the same time with the current logic in BlockPlacementPolicyDefault.chooseTarget().
> One choice we have is to change BlockPlacementPolicyDefault.chooseTarget().
> However, this placement is in general good for all files including the unraided ones.
> It is not clear to us that we can make this good for both raided and unraided files.
> So we propose this idea that when raiding the file. We create one more off-rack replica (so the replication=4 now).
> Than we delete two blocks using the policy in MAPREDUCE-1831 after that (replication=2 now).
> This way we can rearrange the replicas to satisfy (a) and (b) at the same time.

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