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From "Sanjay Radia (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1073) Simpler model for Namenode's fs Image and edit Logs
Date Tue, 13 Apr 2010 22:01:59 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1073?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12856646#action_12856646
] 

Sanjay Radia commented on HDFS-1073:
------------------------------------


># Checkpointing node issues beginCheckpoint to NN
This is backwards (also in the original secondary NN). The NN, not the BNN, should decide
when to do the checkpoint.
Further the NN should tell one of the BNN that he is the checkpointer and simplly write a
special transaction in the edit logs 
"edits is rolled". This special record  indicates to the BNN,  if he is also playing the role
of the checkpointer,  that a checkpoint should be performed.
This has the nice advantage: the last record of rolled edits has a special record at the end
indicating a clean roll or a clean shutdown.

The above works for BOTH designs being propsed (serial # and txid).




> 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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