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From "Rodrigo Schmidt (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-503) Implement erasure coding as a layer on HDFS
Date Thu, 03 Jun 2010 01:12:03 GMT

    [ https://issues.apache.org/jira/browse/HDFS-503?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12874902#action_12874902
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Rodrigo Schmidt commented on HDFS-503:
--------------------------------------

The tags are XML.

There is no documentation for the tags, either.

In short, Raid is still being optimized and changes are constant. Any strong documentation
effort at this point would be meaningful for a very short period of time.

The source code is the best and most precise documentation you can rely upon. That's the good
thing about open source projects. You can easily get around stale documentation.

> 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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