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https://issues.apache.org/jira/browse/HDFS-6701?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14065946#comment-14065946
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Ashwin Shankar commented on HDFS-6701:
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Attached patch creates a new config parameter called
"dfs.namenode.randomize-block-locations-per-block" which can be used to
turn on/off the seed.
> Make seed optional in NetworkTopology#sortByDistance
> ----------------------------------------------------
>
> Key: HDFS-6701
> URL: https://issues.apache.org/jira/browse/HDFS-6701
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Affects Versions: 2.5.0
> Reporter: Ashwin Shankar
> Attachments: HDFS-6701-v1.txt
>
>
> Currently seed in NetworkTopology#sortByDistance is set to the blockid which
> causes the RNG to generate same pseudo random order for each block. If no
> node local block location is present,this causes the same rack local replica
> to be hit for a particular block.
> It'll be good to make the seed optional, so that one could turn it off if
> they want block locations of a block to be randomized.
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