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Date: Fri, 15 Jul 2011 09:23:03 +0000 (UTC)
From: "Ivan Kelly (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HDFS-1073) Simpler model for Namenode's fs
 Image and edit Logs
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    [ https://issues.apache.org/jira/browse/HDFS-1073?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13065801#comment-13065801 ] 

Ivan Kelly commented on HDFS-1073:
----------------------------------

{quote}
LogHeader has a read method but not a write. Will it make sense to encapsulate both read and write of the header in the same class?
Agreed - Ivan has opened HDFS-2149 - I'd propose we do that under that JIRA?
{quote}
HDFS-2149 will probably remove LogHeader completely. I plan to add a getVersion() call to InputStreams and each stream will handle it's own metadata internally. So EditLogFileInputStream will read it's version on creation, or first call to read etc. The input and output stream will be packet based, so an input stream is basically an iterator over FSEditLogOp objects and output stream is a sink for FSEditLogOp objects. I think the way I've implemented the FSEditLogOp objects should avoid all extra copies and object creation. Whats more, there's plenty to room to improve this by removing the creation of ArrayWritables and DeprecatedUTF8 objects and just write strings and arrays directly. 

> 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-editloading-algos.txt, hdfs-1073.txt, hdfs1073.pdf, hdfs1073.pdf, hdfs1073.pdf, hdfs1073.tex
>
>
> 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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