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https://issues.apache.org/jira/browse/HDFS-3544?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14181475#comment-14181475
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liuruoxi commented on HDFS-3544:
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Hey，i m a new learner about hadoop and hdfs-raid，i got a question ，why doesnt
the raid codes be merged into the trunk since release 2.0.2？
> Ability to use SimpleRegeratingCode to fix missing blocks
> ---------------------------------------------------------
>
> Key: HDFS-3544
> URL: https://issues.apache.org/jira/browse/HDFS-3544
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: contrib/raid
> Reporter: dhruba borthakur
>
> ReedSolomon encoding (n, k) has n storage nodes and can tolerate n-k
> failures. Regenerating a block needs to access k blocks. This is a problem
> when n and k are large. Instead, we can use simple regenerating codes (n, k,
> f) that does first does ReedSolomon (n,k) and then does XOR with f stripe
> size. Then, a single disk failure needs to access only f nodes and f can be
> very small.
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