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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5526) Datanode cannot roll back to previous layout version
Date Tue, 19 Nov 2013 22:55:20 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5526?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13827055#comment-13827055
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Kihwal Lee commented on HDFS-5526:
----------------------------------

bq. Would storageID and cTime be preserved?
I think so. The slight difficulty is at loading current/VERSION without blowing up. After
reading in, it needs to override a couple of fields and call writeProperties().

bq. BTW, do you know why cTime=0 in my test case above?
DataStorage's cTime is set to 0 when the node is formatted, but that of BlockPoolSliceStorage
is supposed to be set to the one from nsInfo. So my guess is, when NNStorage is formatted
cTime is 0.  NNStorage.newNamespaceInfo() is setting it to 0 and this must be used for formatting.

> Datanode cannot roll back to previous layout version
> ----------------------------------------------------
>
>                 Key: HDFS-5526
>                 URL: https://issues.apache.org/jira/browse/HDFS-5526
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>            Reporter: Tsz Wo (Nicholas), SZE
>            Assignee: Kihwal Lee
>            Priority: Blocker
>         Attachments: HDFS-5526.patch
>
>
> Current trunk layout version is -48.
> Hadoop v2.2.0 layout version is -47.
> If a cluster is upgraded from v2.2.0 (-47) to trunk (-48), the datanodes cannot start
with -rollback.  It will fail with IncorrectVersionException.



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