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https://issues.apache.org/jira/browse/HDFS-3702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15264590#comment-15264590
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stack commented on HDFS-3702:
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Any chance of getting this on 2.8 branch? Thanks.

> Add an option for NOT writing the blocks locally if there is a datanode on 
> the same box as the client
> -----------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-3702
>                 URL: https://issues.apache.org/jira/browse/HDFS-3702
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: hdfs-client
>    Affects Versions: 2.5.1
>            Reporter: Nicolas Liochon
>            Assignee: Lei (Eddy) Xu
>            Priority: Minor
>              Labels: BB2015-05-TBR
>             Fix For: 3.0.0, 2.9.0
>
>         Attachments: HDFS-3702.000.patch, HDFS-3702.001.patch, 
> HDFS-3702.002.patch, HDFS-3702.003.patch, HDFS-3702.004.patch, 
> HDFS-3702.005.patch, HDFS-3702.006.patch, HDFS-3702.007.patch, 
> HDFS-3702.008.patch, HDFS-3702.009.patch, HDFS-3702.010.patch, 
> HDFS-3702.011.patch, HDFS-3702.012.patch, HDFS-3702_Design.pdf
>
>
> This is useful for Write-Ahead-Logs: these files are writen for recovery 
> only, and are not read when there are no failures.
> Taking HBase as an example, these files will be read only if the process that 
> wrote them (the 'HBase regionserver') dies. This will likely come from a 
> hardware failure, hence the corresponding datanode will be dead as well. So 
> we're writing 3 replicas, but in reality only 2 of them are really useful.



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