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https://issues.apache.org/jira/browse/HDFS-9833?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15295644#comment-15295644
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Rakesh R commented on HDFS-9833:
--------------------------------
[~drankye], Attached patch is addressing basic checksum recalculation of a
whole block reconstruction. Like we discussed earlier in this jira, could raise
subsequent sub tasks for handling the following cases once the basic patch is
in.
# handling multiple block failures within a block group.
# handling partial block reconstruction and recalculate checksum. I meant,
getting checksum for a particular range less than file size cases.
Note: Test case failure is unrelated to the patch and this failure will be
addressed using HDFS-10434.
> 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
>
>
> 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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