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https://issues.apache.org/jira/browse/HDFS-8945?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14712887#comment-14712887
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Masatake Iwasaki commented on HDFS-8945:
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Hmm.. Storage policies wins because rack awareness always fallback to random
but storage policy is must.
{{BlockPlacementPolicyDefault}} looks for node based on network topology at
first, then checks the chosen node has required storage type. If the node does
not satisfy the storage condition, then the next node is selected along with
the rule of rack awareness. If enough replicas are not found in the first path,
it look for the nodes having fallback storage types defined in the policy in
the second path.
> Update the description about replica placement in HDFS Architecture
> documentation
> ---------------------------------------------------------------------------------
>
> Key: HDFS-8945
> URL: https://issues.apache.org/jira/browse/HDFS-8945
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: documentation
> Reporter: Masatake Iwasaki
> Assignee: Masatake Iwasaki
> Priority: Minor
> Attachments: HDFS-8945.001.patch
>
>
> The description about replica placement should have
> * Explanation about storage types and storage policies should be added
> * placement policy for replication factor greater than 4
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