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From "Konstantin Shvachko (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-227) Namespace check pointing is not performed until the namenode restarts.
Date Tue, 28 Nov 2006 02:54:23 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-227?page=comments#action_12453781 ] 
Konstantin Shvachko commented on HADOOP-227:

Complex rename relocation stuff could be avoided if we used (unique) files ids to identify
In this case file name is just an attribute of the file. Renaming does not change the file
File hierarchy is based on ids rather than file names.
And if we need to sort, we sort by file ids rather than their names.

I like the merging approach. It is simple in general (not in details though) and does not
involve introducing additional structures in the name-node, which will be hard to support,
especially if we plan to replace global locking by something more elaborate.
And best of all it can work as a separate component.

> Namespace check pointing is not performed until the namenode restarts.
> ----------------------------------------------------------------------
>                 Key: HADOOP-227
>                 URL: http://issues.apache.org/jira/browse/HADOOP-227
>             Project: Hadoop
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.2.0
>            Reporter: Konstantin Shvachko
>         Assigned To: Milind Bhandarkar
> In current implementation when the name node starts, it reads its image file, then
> the edits file, and then saves the updated image back into the image file.
> The image file is never updated after that.
> In order to provide the system reliability reliability the namespace information should
> be check pointed periodically, and the edits file should be kept relatively small.

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