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From "Lei (Eddy) Xu (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-3702) Add an option for NOT writing the blocks locally if there is a datanode on the same box as the client
Date Thu, 10 Mar 2016 19:50:40 GMT

     [ https://issues.apache.org/jira/browse/HDFS-3702?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Lei (Eddy) Xu updated HDFS-3702:
--------------------------------
    Release Note: This patch will attempt to allocate all replicas to remote DataNodes, by
adding local DataNode to the excluded DataNodes. If no sufficient replicas can be obtained,
it will fall back to default block placement policy, which writes one replica to local DataNode.

> 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, HDFS-3702.006.patch, HDFS-3702.007.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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