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https://issues.apache.org/jira/browse/HDFS-503?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12873589#action_12873589
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Rodrigo Schmidt commented on HDFS-503:
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raid1.txt and raid2.txt are different patches. The most recent was the one that
got committed.
Raid is implementing simple xor parity right now, but we have plans to extend
it in the future.
Sorry, no design diagrams that I'm aware of.
> 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: 0.21.0
>
> 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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