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https://issues.apache.org/jira/browse/HDFS-7891?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14366860#comment-14366860
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Walter Su commented on HDFS-7891:
---------------------------------
I upload a new patch {{HDFS-7891.003.patch}}. It use random policy with
{{maxNodesPerRack}} .
*Design*
R = total racks in cluster
X = total expected replicas
Q=Math.floor(X/R)
T=X%R
if X<R, X racks have 1 replica.
if X>R && T==0, R racks have Q replicas.
if X>R && T!=0,, X-T racks have Q replicas. T racks have Q+1 replicas.
*Coding*
1. Add a function getMaxNodesPerRack(..)
2. Call getMaxNodesPerRack(..) before every choosing
*Defects*
I copy a lot of code from {{BlockPlacementPolicyDefault}} . If I didn't do
this, I have to modify {{BlockPlacementPolicyDefault}} so it can call an empty
getMaxNodesPerRack(..) before every choosing, and I can overide it on child
class.
> 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.patch, PlacementPolicyBenchmark.txt, testresult.txt
>
>
> a block placement policy tries its best to place replicas to most racks.
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