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From "Jitendra Nath Pandey (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1371) One bad node can incorrectly flag many files as corrupt
Date Thu, 14 Apr 2011 01:06:05 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1371?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13019650#comment-13019650
] 

Jitendra Nath Pandey commented on HDFS-1371:
--------------------------------------------

> any drawbacks of this approach? Keeps namenode complexity down, prevents DOS, etc.

  The only drawback I can think of is that the namenode will continue to serve this replica
to clients until datanode reports that it is corrupt. But, there is already a window of time
when multiple clients can try to read a corrupt replica. This approach will increase that
window (probably by a few seconds). It seems to be a justified cost to avoid DOS and additional
complexity in namenode.

> One bad node can incorrectly flag many files as corrupt
> -------------------------------------------------------
>
>                 Key: HDFS-1371
>                 URL: https://issues.apache.org/jira/browse/HDFS-1371
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs client, name-node
>    Affects Versions: 0.20.1
>         Environment: yahoo internal version 
> [knoguchi@gwgd4003 ~]$ hadoop version
> Hadoop 0.20.104.3.1007030707
>            Reporter: Koji Noguchi
>            Assignee: Tanping Wang
>
> On our cluster, 12 files were reported as corrupt by fsck even though the replicas on
the datanodes were healthy.
> Turns out that all the replicas (12 files x 3 replicas per file) were reported corrupt
from one node.
> Surprisingly, these files were still readable/accessible from dfsclient (-get/-cat) without
any problems.

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