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From "Sameer Paranjpye (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-334) Redesign the dfs namespace datastructures to be copy on write
Date Tue, 07 Nov 2006 01:41:38 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-334?page=comments#action_12447602 ] 
Sameer Paranjpye commented on HADOOP-334:

Yes, a sequence number is more robust in the face of time rollbacks. W.r.t the comment on
transaction 'm' and how it affects transaction 'x', if we say that:

A transaction in the edits log applies to the namespace iff:
a. the sequence number on the transaction is higher than the sequence number of the node that
it affects OR
b. if the node does not exist in the namespace the sequence number of the transaction is more
recent than that of the closest existing ancestor

then it should work.

> 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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