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https://issues.apache.org/jira/browse/HDFS-3702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15205215#comment-15205215
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Tsz Wo Nicholas Sze commented on HDFS-3702:
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> For uniform distribution of files over a cluster, I think users would prefer
> that DFSClient managed it for them (a new flag on CreateFlag?) ...
How would DFSClient know which nodes are disfavored nodes? How could it
enforce disfavored nodes?
> ... disfavoredNodes seems like a more intrusive and roundabout route – with
> its overrides, possible builders, and global interpretation of 'localhost'
> string – to the clean flag this patch carries?
I disagree. Since we already have favoredNodes, adding disfavoredNodes seems
more natural than adding a flag.
In addition, the new FileSystem CreateFlag does not look clean to me since it
is too specific to HDFS. How would other FileSystems such as LocalFileSystem
implement it?
> 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-3702.008.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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