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https://issues.apache.org/jira/browse/HDFS-7891?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14379598#comment-14379598
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Tsz Wo Nicholas Sze commented on HDFS-7891:
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Hi Walter, thanks for working on this JIRA. For replication, we allow 2
replicas stored under the same rack. How about we do the same for EC block
group?
I understand that the current approach tries to do best fault tolerance.
However, it may not be the best policy in practice since such policy generates
more remote rack traffic. Also (6,3)-Reed-Solomon already can tolerate one
more failure compared to 3-replication. I think the default block placement
policy should allow maximum 2 replicas per rack. What do you think?
> A block placement policy with best fault tolerance
> --------------------------------------------------
>
> Key: HDFS-7891
> URL: https://issues.apache.org/jira/browse/HDFS-7891
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Walter Su
> Assignee: Walter Su
> Attachments: HDFS-7891.002.patch, HDFS-7891.003.patch,
> HDFS-7891.004.patch, HDFS-7891.patch, PlacementPolicyBenchmark.txt,
> testresult.txt
>
>
> a block placement policy tries its best to place replicas to most racks.
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