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https://issues.apache.org/jira/browse/HDFS-11190?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15972501#comment-15972501
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Ewan Higgs commented on HDFS-11190:
-----------------------------------
This is a good change that can probably go into the branch. Some things that
should be discussed before merging with trunk:
BlockStoragePolicySuite.java
Why {{PROVIDED}}, {{DISK}} and not {{DISK}}, {{PROVIDED}}?
In ProvidedStorageMap.java we make a DatanodeStorage using {{NORMAL}},
{{PROVIDED}} (line 86), so it seems that this is a good ordering.
Changing this requires a change in TestBlockStoragePolicy (line 144) as well.
Also, especially since LocatedBlock moved {{PROVIDED}} to the end anyway, why
not begin with storagePolicy with {{PROVIDED}} at the end so the
{{moveProvidedToEnd}} becomes a no-op.
LocatedBlock.java
Shorten {{moveProvidedToEnd}} to use Arrays.sort(T[], Comparator) which is
stable. Comparator can just return Provided > anything else.
https://docs.oracle.com/javase/7/docs/api/java/util/Arrays.html#sort(T[],%20java.util.Comparator)
If we don't do this, then we should add more checks to test that the algorithm
is correct.
> [READ] Namenode support for data stored in external stores.
> -----------------------------------------------------------
>
> Key: HDFS-11190
> URL: https://issues.apache.org/jira/browse/HDFS-11190
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Virajith Jalaparti
> Attachments: HDFS-11190-HDFS-9806.001.patch,
> HDFS-11190-HDFS-9806.002.patch, HDFS-11190-HDFS-9806.003.patch
>
>
> The goal of this JIRA is to enable the Namenode to know about blocks that are
> in {{PROVIDED}} stores and are not necessarily stored on any Datanodes.
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