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https://issues.apache.org/jira/browse/HDFS-7621?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14506368#comment-14506368
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Walter Su commented on HDFS-7621:
---------------------------------
001 patch is initial patch. No tests included. I want to know if the logic
works.
What does the patch do:
1. {{Balancer.isGoodBlockCandidate(..)}} is a guard function. The patch make
the function take EC block group into consideration. It can avoid place 2
block ( of BlockGroup ) in same node. {{reduceNumOfRacks(..)}} guard can avoid
reduce number of racks after movement, so it tries not to violate (specific)
placement policy but can't guarantee.
How does the patch work:
Balancer doesn't know EC Block group, it only know reported block( with real
blockId in datanode). But I want it to take the locations of the group into
consideration when choosing targets.
It requires the correctness of {{DBlock.isLocatedOn(..)}} HDFS-8147 .
> Erasure Coding: update the Balancer/Mover data migration logic
> --------------------------------------------------------------
>
> Key: HDFS-7621
> URL: https://issues.apache.org/jira/browse/HDFS-7621
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Jing Zhao
> Assignee: Walter Su
> Attachments: HDFS-7621.001.patch
>
>
> Currently the Balancer/Mover only considers the distribution of replicas of
> the same block during data migration: the migration cannot decrease the
> number of racks. With EC the Balancer and Mover should also take into account
> the distribution of blocks belonging to the same block group.
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