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Date: Tue, 1 Jun 2010 15:05:36 -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:
----------------------------------

        Summary: Delete the co-located replicas when raiding file  (was: Delete the replica on the most concentrated node when raiding file)
    Description: 
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.

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.

  was:
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.

One way to do this is that we can add a new BlockPlacementPolicy which delete the replicas that are co-located.
So when raiding the file, we can make the remaining replicas live on different machines.


> 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
>
>
> 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.
> 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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