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From "Walter Su (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7891) A block placement policy with best fault tolerance
Date Fri, 27 Mar 2015 01:43:54 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7891?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14383187#comment-14383187
] 

Walter Su commented on HDFS-7891:
---------------------------------

If we put 2 replicas on local rack during file creation, 1 LN + 1 LR + RR_1 + RR_2 + RR_3
+ RR_4..... Only local rack is allowed 2 replica, and remote rack is allowed 1 replica. We
can tolerant 2 racks failure(out of 8 racks). It reduces 1 rack traffic during file creation,
but will not during Reconstruction.
If we put 2 replicas on every racks during file creation and Reconstruction. 1 LN + 1 LR +
RR_1 + RR_1 + RR_2 + RR_2. Both file creation and Reconstruction process  can reduce 1 rack
traffic. We can tolerant 1 rack failure(out of 4 racks).
The default policy can tolerant 1 rack failure(out of 2 racks).


> 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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