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https://issues.apache.org/jira/browse/HDFS-900?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12935471#action_12935471
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Todd Lipcon commented on HDFS-900:
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Yes, I believe this reproduces in 0.21 and 0.22 (the to-reproduce.patch was
against trunk at the time though likely is out of date now)
> Corrupt replicas are not tracked correctly through block report from DN
> -----------------------------------------------------------------------
>
> Key: HDFS-900
> URL: https://issues.apache.org/jira/browse/HDFS-900
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 0.22.0
> Reporter: Todd Lipcon
> Priority: Critical
> Attachments: log-commented, to-reproduce.patch
>
>
> This one is tough to describe, but essentially the following order of events
> is seen to occur:
> # A client marks one replica of a block to be corrupt by telling the NN about
> it
> # Replication is then scheduled to make a new replica of this node
> # The replication completes, such that there are now 3 good replicas and 1
> corrupt replica
> # The DN holding the corrupt replica sends a block report. Rather than
> telling this DN to delete the node, the NN instead marks this as a new *good*
> replica of the block, and schedules deletion on one of the good replicas.
> I don't know if this is a dataloss bug in the case of 1 corrupt replica with
> dfs.replication=2, but it seems feasible. I will attach a debug log with some
> commentary marked by '============>', plus a unit test patch which I can get
> to reproduce this behavior reliably. (it's not a proper unit test, just some
> edits to an existing one to show it)
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