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From "Hairong Kuang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1508) Ability to do savenamespace without being in safemode
Date Fri, 10 Dec 2010 01:05:02 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1508?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12970036#action_12970036
] 

Hairong Kuang commented on HDFS-1508:
-------------------------------------

Sanjay, your table summarized all the scenarios. But this jira does not invent a new operation
saveNamespace. Most cases have already been addressed by the existing code.

The only new scenario that this jira introduces is that if savenamespace fails, checkpointing
can still continue to run and may corrupt the image. So I suggested to put namenode in safemode
if savenamespace fails. This makes sense operationally because something that's critical to
NameNode happens, NameNode should stop operation and waits for admin's intervention.

> Ability to do savenamespace without being in safemode
> -----------------------------------------------------
>
>                 Key: HDFS-1508
>                 URL: https://issues.apache.org/jira/browse/HDFS-1508
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>         Attachments: savenamespaceWithoutSafemode.txt, savenamespaceWithoutSafemode2.txt,
savenamespaceWithoutSafemode3.txt, savenamespaceWithoutSafemode4.txt
>
>
> In the current code, the administrator can run savenamespace only after putting the namenode
in safemode. This means that applications that are writing to HDFS encounters errors because
the NN is in safemode. We would like to allow saveNamespace even when the namenode is not
in safemode.
> The savenamespace command already acquires the FSNamesystem writelock. There is no need
to require that the namenode is in safemode too.

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