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https://issues.apache.org/jira/browse/MAPREDUCE-3361?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13162247#comment-13162247
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Alex Dimakis commented on MAPREDUCE-3361:
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After some discussion, it seems that the easiest method to ensure backwards
compatibility is to recognize if this is a Reed-Solomon coded packet or an SRC
coded packet by the size of the parity file. If we use stripe size 10, 4 RS
packets and 2 simple XORs then the parity file should have size 64MB*6 while
for RS coded files it should be 64MB*4. We will implement this distinction in
Processfile and run different decoder functions accordingly.
> Ability to use SimpleRegeratingCode to fix missing blocks
> ---------------------------------------------------------
>
> Key: MAPREDUCE-3361
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-3361
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: contrib/raid
> Reporter: dhruba borthakur
> Assignee: 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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