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From "J.Andreina (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9044) Give Priority to FavouredNodes , before selecting nodes from FavouredNode's Node Group
Date Tue, 22 Sep 2015 12:19:04 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9044?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14902475#comment-14902475
] 

J.Andreina commented on HDFS-9044:
----------------------------------

Testcase failures are unrelated. 
Checkstyle comments can be ignored , as all the 9 parameters of the method are been used.
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
>
>
> 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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