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https://issues.apache.org/jira/browse/HDFS-9833?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15298145#comment-15298145
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Rakesh R commented on HDFS-9833:
--------------------------------

Hi, [~drankye], [~umamaheswararao] would be great to see feedback on the latest 
patch. I will create separate jira tasks if you agree on [tasks split 
up|https://issues.apache.org/jira/browse/HDFS-9833?focusedCommentId=15295644&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15295644]
 mentioned earlier in this jira and will try to push this basic patch in. 
Thanks!

Note: I feel the checkstyle warning can be ignored, if needed will rename the 
args in next patch preparation time. Also, the test case failure is unrelated 
to my patch.

> Erasure coding: recomputing block checksum on the fly by reconstructing the 
> missed/corrupt block data
> -----------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-9833
>                 URL: https://issues.apache.org/jira/browse/HDFS-9833
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Kai Zheng
>            Assignee: Rakesh R
>              Labels: hdfs-ec-3.0-must-do
>         Attachments: HDFS-9833-00-draft.patch, HDFS-9833-01.patch, 
> HDFS-9833-02.patch, HDFS-9833-03.patch, HDFS-9833-04.patch
>
>
> As discussed in HDFS-8430 and HDFS-9694, to compute striped file checksum 
> even some of striped blocks are missed, we need to consider recomputing block 
> checksum on the fly for the missed/corrupt blocks. To recompute the block 
> checksum, the block data needs to be reconstructed by erasure decoding, and 
> the main needed codes for the block reconstruction could be borrowed from 
> HDFS-9719, the refactoring of the existing {{ErasureCodingWorker}}. In EC 
> worker, reconstructed blocks need to be written out to target datanodes, but 
> here in this case, the remote writing isn't necessary, as the reconstructed 
> block data is only used to recompute the checksum.



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