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Posted to hdfs-issues@hadoop.apache.org by "Allen Wittenauer (JIRA)" <ji...@apache.org> on 2014/07/21 20:12:42 UTC

[jira] [Commented] (HDFS-125) Consistency of different replicas of the same block is not checked.

    [ https://issues.apache.org/jira/browse/HDFS-125?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14068950#comment-14068950 ] 

Allen Wittenauer commented on HDFS-125:
---------------------------------------

This feels like a special case of the problems mentioned in HDFS-366 .

> Consistency of different replicas of the same block is not checked.
> -------------------------------------------------------------------
>
>                 Key: HDFS-125
>                 URL: https://issues.apache.org/jira/browse/HDFS-125
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: Konstantin Shvachko
>
> HDFS currently detects corrupted replicas by verifying that its contents matches the checksum stored in the block meta-file. This is done independently for each replica of the block on the data-node it belongs to. But we do not check that the replicas are identical across data-nodes as long as they have the same size.
> This is not common but can happen as a result of a software bug or an operator mismanagement. And in this case different clients will read different data from the same file.



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