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From "Zooko Wilcox-O'Hearn (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-503) Implement erasure coding as a layer on HDFS
Date Tue, 06 Oct 2009 14:57:31 GMT

    [ https://issues.apache.org/jira/browse/HDFS-503?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12762652#action_12762652

Zooko Wilcox-O'Hearn commented on HDFS-503:

By the way the hadoop-lafs plugin for Hadoop also provides erasure coding, by using the Tahoe
Least-Authority Filesystem instead of HDFS: http://code.google.com/p/hadoop-lafs/ .  The erasure
coding in Tahoe-LAFS is implemented with a high-speed Reed-Solomon implementation in C.

> 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
> 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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