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https://issues.apache.org/jira/browse/HDFS-3702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15187937#comment-15187937
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Andrew Wang commented on HDFS-3702:
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Hey Eddy, thanks for reworking, a few comments:
* Is BlockPlacementFlag being used in hadoop-common? Seems like it should go in
hadoop-hdfs instead.
* Can we name BlockPlacementFlag "AddBlockFlag" instead? That's more
future-proof, since it doesn't restrict us to just BPP-related flags.
* Can we hook into BlockPlacementPolicyDefault the same way as HDFS-4946? i.e.
where the {{preferLocalNode}} boolean is used. It'd be good to implement these
two features the same way, though it does require threading the state all the
way down.
* Nit: ClientProtocol "advice" -> "advise", though this might change after
renaming to AddBlockFlag.
> 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
> 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
>
>
> 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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