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From "Owen O'Malley (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-334) Redesign the dfs namespace datastructures to be copy on write
Date Mon, 06 Nov 2006 21:57:44 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-334?page=comments#action_12447550 ] 
            
Owen O'Malley commented on HADOOP-334:
--------------------------------------

Sameer, you missed the point. You don't need any locks for checkpointing with copy on write
other than a quick read lock on the root while you switch to a new log. Once you have started
the new log, you can traverse from the old root and see the state at the transition. So the
lock is held while you open a single file.

> Redesign the dfs namespace datastructures to be copy on write
> -------------------------------------------------------------
>
>                 Key: HADOOP-334
>                 URL: http://issues.apache.org/jira/browse/HADOOP-334
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: dfs
>    Affects Versions: 0.4.0
>            Reporter: Owen O'Malley
>         Assigned To: Konstantin Shvachko
>
> The namespace datastructures should be copy on write so that the namespace does not need
to be completely locked down from user changes while the checkpoint is being made.

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