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https://issues.apache.org/jira/browse/HADOOP-1838?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12525549
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Hadoop QA commented on HADOOP-1838:
-----------------------------------

+1

http://issues.apache.org/jira/secure/attachment/12365210/blockSizeZero.patch 
applied and successfully tested against trunk revision r573383.

Test results:   
http://lucene.zones.apache.org:8080/hudson/job/Hadoop-Patch/698/testReport/
Console output: 
http://lucene.zones.apache.org:8080/hudson/job/Hadoop-Patch/698/console

> Files created with an pre-0.15 gets blocksize as zero, causing performance 
> degradation
> --------------------------------------------------------------------------------------
>
>                 Key: HADOOP-1838
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1838
>             Project: Hadoop
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.15.0
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>            Priority: Blocker
>             Fix For: 0.15.0
>
>         Attachments: blockSizeZero.patch
>
>
> HADOOP-1656 introduced the support for storing block size persistently as 
> inode metadata. Previously, if the file has only one block then it was not 
> possible to accurately determine the blocksize that the application has 
> requested at file-creation time.
> The upgrade of an older layout to the new layout kept the blocksize as zero 
> for single-block files that were upgraded to the new layout. This was done to 
> indicate the DFS really does not know the "true" blocksize of this file. This 
> caused map-reduce to determine that a split is 1 byte in length!

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