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From "Zhe Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7891) A block placement policy with best fault tolerance
Date Wed, 25 Mar 2015 19:16:54 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7891?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14380569#comment-14380569

Zhe Zhang commented on HDFS-7891:

[~walter.k.su] Below are my comments about 004 patch:
# I guess the performance should be similar to {{BlockPlacementPolicyDefault}}?
# The {{getAdaptiveMaxNodesPerRack}} method is a little awkward: among the 3 arguments, the
super method uses 1 and the subclass uses the other 2. 
# The {{chooseTargetInOrder}} method in both super class and subclass look good to me.
# Can we just override {{getMaxNodesPerRack}} with the logic in {{BlockPlacementPolicyFaultTolerant#getAdaptiveMaxNodesPerRack}}?
If necessary we can change its signature.

In general, I agree it's a good idea to have a simple solution with clean code structure first,
and worry about performance later (if we observe an performance issue we can always add the
sorted rack method back).

> 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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