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From "Konstantin Shvachko (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1073) Simpler model for Namenode's fs Image and edit Logs
Date Fri, 05 Nov 2010 05:55:48 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1073?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12928488#action_12928488
] 

Konstantin Shvachko commented on HDFS-1073:
-------------------------------------------

- Sanjay, Todd means that when a checkpoint starts it triggers rollEdits(), which is the cut
off point for the new checkpoint. The checkpoint of course can use the latest rolled edits
instead, but then you get the problem of synchronizing the start of a checkpoint and the edits
roll event. Otherwise checkpoints may become way behind the current namespace state.
- I agree with Rob that edits_100-100 should not be a special case to avoid. In practice we
will not see it, but if it happens the system should just absorb it. Todd correctly points
out that if the system is idle for a very long time NN may try to create edits_100-100 the
second time, but this could be just avoided based on name collision.
- I do not see or did not understand the rational for "I'm quitting!" record. Why should NN
care whether last record was lost or not, just keep going with what it has. Worked so far.

> 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
>         Attachments: hdfs-1073.txt, hdfs1073.pdf
>
>
> 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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