[jira] [Commented] (HDFS-9833) Erasure coding: recomputing block checksum on the fly by reconstructing the missed/corrupt block data

["Kai Zheng (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDFS-9833?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15249965#comment-15249965 ] 

Kai Zheng commented on HDFS-9833:
---------------------------------

Per off-line discussion with [~rakeshr], he'd like to help with this and so reassigned. Thanks Rakesh for the taking!

> 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
>
> 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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