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From "Sanjay Radia (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1508) Ability to do savenamespace without being in safemode
Date Wed, 01 Dec 2010 03:18:13 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1508?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12965556#action_12965556
] 

Sanjay Radia commented on HDFS-1508:
------------------------------------

> saveNamespace with -f to indicate that NN should automatically enter safe mode
I was suggesting that -f implies that even though it is not in safemode go ahead (without
putting it in safemode). The motivation being that doing saveNamespace is a big deal as could
make the NN unresponsive for a while.

I had not thought about the checkpoint issue that Kons mentioned. If saveNamespace comes in
the middle of a checkpoint then can the NN ignore the checkpoint sent by secondary?
(BTW with HDFS-1073 this problem disappears - one can take as many checkpoint as one likes).
If it complicates the BNN/SNN's checkpoint then this Jira should wait till 1073 is done.

As far as motivation: Ops wants to do a checkpoint without the BNN/SNN (say it is down) and
is willing to make the NN unresponsive for a short while.


> 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
>
>
> 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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