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https://issues.apache.org/jira/browse/HDFS-11160?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15680593#comment-15680593
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Wei-Chiu Chuang commented on HDFS-11160:
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HDFS-11022 is the aftermath of this bug. VolumeScanner detects corruption
incorrectly, and then it reports the older replica gen stamp to NameNode (the
replica is updated while VolumeScanner is scanning).
> VolumeScanner incorrectly reports good replicas as corrupt due to race
> condition
> --------------------------------------------------------------------------------
>
> Key: HDFS-11160
> URL: https://issues.apache.org/jira/browse/HDFS-11160
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Environment: CDH5.7.4
> Reporter: Wei-Chiu Chuang
> Assignee: Wei-Chiu Chuang
> Attachments: HDFS-11160.reproduce.patch
>
>
> Due to a race condition initially reported in HDFS-6804, VolumeScanner may
> erroneously detect good replicas as corrupt. This is serious because in some
> cases it results in data loss if all replicas are declared corrupt.
> We are investigating an incidence that caused very high block corruption rate
> in a relatively small cluster. Initially, we thought HDFS-11056 is to blame.
> However, after applying HDFS-11056, we are still seeing VolumeScanner
> reporting corrupt replicas.
> It turns out that if a replica is being appended while VolumeScanner is
> scanning it, VolumeScanner may use the new checksum to compare against old
> data, causing checksum mismatch.
> I have a unit test to reproduce the error. Will attach later.
> To fix it, I propose a FinalizedReplica object should also have a
> lastChecksum field like ReplicaBeingWritten, and BlockSender should use the
> in-memory lastChecksum to verify the partial data in the last chunk on disk.
> File this jira to discuss a good fix for this issue.
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