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From "Hairong Kuang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1103) Replica recovery doesn't distinguish between flushed-but-corrupted last chunk and unflushed last chunk
Date Fri, 14 May 2010 03:44:43 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1103?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12867381#action_12867381
] 

Hairong Kuang commented on HDFS-1103:
-------------------------------------

I do not think that this is the case in 0.21 & the trunk. In our lease recovery algorithm
in 0.21, If there are 2 RBWs and 1 RWR, 1 RWR is excluded from the lease recovery. In the
scenario that you described, RBW B and RBW C's GS is bumped and the length of recovered two
replicas is truncated to MIN( len(B), len(C)).

> Replica recovery doesn't distinguish between flushed-but-corrupted last chunk and unflushed
last chunk
> ------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-1103
>                 URL: https://issues.apache.org/jira/browse/HDFS-1103
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: data-node
>    Affects Versions: 0.21.0, 0.22.0
>            Reporter: Todd Lipcon
>            Priority: Blocker
>         Attachments: hdfs-1103-test.txt
>
>
> When the DN creates a replica under recovery, it calls validateIntegrity, which truncates
the last checksum chunk off of a replica if it is found to be invalid. Then when the block
recovery process happens, this shortened block wins over a longer replica from another node
where there was no corruption. Thus, if just one of the DNs has an invalid last checksum chunk,
data that has been sync()ed to other datanodes can be lost.

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