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https://issues.apache.org/jira/browse/HDFS-503?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12762553#action_12762553
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Hudson commented on HDFS-503:
-----------------------------

Integrated in Hadoop-Hdfs-trunk-Commit #61 (See 
[http://hudson.zones.apache.org/hudson/job/Hadoop-Hdfs-trunk-Commit/61/])
    . This patch implements an optional layer over HDFS that 
implements offline erasure-coding.  It can be used to reduce the 
total storage requirements of HDFS.  (dhruba)


> Implement erasure coding as a layer on HDFS
> -------------------------------------------
>
>                 Key: HDFS-503
>                 URL: https://issues.apache.org/jira/browse/HDFS-503
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: contrib/raid
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>             Fix For: 0.22.0
>
>         Attachments: raid1.txt, raid2.txt
>
>
> The goal of this JIRA is to discuss how the cost of raw storage for a HDFS 
> file system can be reduced. Keeping three copies of the same data is very 
> costly, especially when the size of storage is huge. One idea is to reduce 
> the replication factor and do erasure coding of a set of blocks so that the 
> over probability of failure of a block remains the same as before.
> Many forms of error-correcting codes are available, see 
> http://en.wikipedia.org/wiki/Erasure_code. Also, recent research from CMU has 
> described DiskReduce 
> https://opencirrus.org/system/files/Gibson-OpenCirrus-June9-09.ppt.
> My opinion is to discuss implementation strategies that are not part of base 
> HDFS, but is a layer on top of HDFS.

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