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https://issues.apache.org/jira/browse/CASSANDRA-6268?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13808368#comment-13808368
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Jonathan Ellis commented on CASSANDRA-6268:
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We closed CASSANDRA-6124 in favor of adding LOCAL_ONE; I can't think of a case
where you'd want to span more than one DC but less than all.
> Poor performance of Hadoop if any DC is using VNodes
> ----------------------------------------------------
>
> Key: CASSANDRA-6268
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6268
> Project: Cassandra
> Issue Type: Improvement
> Components: Hadoop
> Reporter: Piotr Kołaczkowski
> Assignee: Piotr Kołaczkowski
> Attachments:
> 0001-DSP-2572-Adds-ability-to-set-target-DCs-where-a-Hado.patch
>
>
> Some customers are complaining about huge number of splits in Hadoop caused
> by VNodes. Disabling vnodes only in Hadoop DC does not fix it, because splits
> are generated from the results of describe_ring, which returns a huge number
> of ranges.
> The proposed fix:
> - allows for specifying the DCs the Hadoop job should be run
> - merges the consecutive ranges before generating Hadoop splits, so we don't
> have artificial range splitting caused by vnodes in the other DCs
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