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https://issues.apache.org/jira/browse/HDFS-9044?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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J.Andreina updated HDFS-9044:
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Attachment: HDFS-9044.4.patch
Updated the patch.
Please review.
> Give Priority to FavouredNodes , before selecting nodes from FavouredNode's
> Node Group
> --------------------------------------------------------------------------------------
>
> Key: HDFS-9044
> URL: https://issues.apache.org/jira/browse/HDFS-9044
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: J.Andreina
> Assignee: J.Andreina
> Attachments: HDFS-9044.1.patch, HDFS-9044.2.patch, HDFS-9044.3.patch,
> HDFS-9044.4.patch
>
>
> Passing Favored nodes intention is to place replica among the favored node
> Current behavior in Node group is
> If favored node is not available it goes to one among favored
> nodegroup.
> {noformat}
> Say for example:
> 1)I need 3 replicas and passed 5 favored nodes.
> 2)Out of 5 favored nodes 3 favored nodes are not good.
> 3)Then based on BlockPlacementPolicyWithNodeGroup out of 5 targets node
> returned , 3 will be random node from 3 bad FavoredNode's nodegroup.
> 4)Then there is a probability that all my 3 replicas are placed on
> Random node from FavoredNodes's nodegroup , instead of giving priority to 2
> favored nodes returned as target.
> {noformat}
> *Instead of returning 5 targets on 3rd step above , we can return 2 good
> favored nodes as target*
> *And remaining 1 needed replica can be chosen from Random node of bad
> FavoredNodes's nodegroup.*
> This will make sure that the FavoredNodes are given priority.
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