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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1508) Ability to do savenamespace without being in safemode
Date Sat, 04 Dec 2010 00:44:13 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1508?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12966759#action_12966759
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dhruba borthakur commented on HDFS-1508:
----------------------------------------

> This addresses Konstanitin's request to add a unit test to test the invocation of saveNamespace
command in the middle of a checkpoint.

Unit test was already part of the last patch I uploaded.

> needs some convincing argumentation, which is hard.
I am trying to explain this again: checkpointing occurs every half hour or so. if one of the
name.dir directory goes bad, then the namenode is like running on a spare tire. It is better
not to wait for the next half hour to replace the spare-tire, but better to fix it right away.
Especially important when you are running a realtime load via HBase on HDFS!


> 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
>
>
> 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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