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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1073) Simpler model for Namenode's fs Image and edit Logs
Date Mon, 05 Apr 2010 08:19:28 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1073?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12853337#action_12853337

Todd Lipcon commented on HDFS-1073:

I began working on this tonight and came upon another pro for the sequential numbering of
the logs:

There may be occasional times when we want to roll the edit log when we've not made any edits
into it. For example, if the NN has started but no edits have been made yet, and the 2NN wants
to start a checkpoint, it will ask the NN to roll the edits log. In the sequential design,
this means it will roll from edits_N to edits_N+1 even if edits_N is empty - the 2NN then
downloads the empty edits_N and everything works as expected. If we used txids, there would
be no new filename to move to, and we'd have to add special logic to detect this case in various

> Simpler model for Namenode's fs Image and edit Logs 
> ----------------------------------------------------
>                 Key: HDFS-1073
>                 URL: https://issues.apache.org/jira/browse/HDFS-1073
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Sanjay Radia
>            Assignee: Todd Lipcon
> The naming and handling of  NN's fsImage and edit logs can be significantly improved
resulting simpler and more robust code.

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