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Message-ID: <12722991.70621276821564875.JavaMail.jira@thor>
Date: Thu, 17 Jun 2010 20:39:24 -0400 (EDT)
From: "Scott Chen (JIRA)" <jira@apache.org>
To: mapreduce-issues@hadoop.apache.org
Subject: [jira] Updated: (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:all-tabpanel ]

Scott Chen updated MAPREDUCE-1831:
----------------------------------

    Status: Patch Available  (was: Open)

I think the failed contrib test may be TestSimulatorDeterministicReplay.testMain.
It is a know issue in MAPREDUCE-1834.

But the testReport is gone.
I am submitting this to hudson again.


> 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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