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https://issues.apache.org/jira/browse/CASSANDRA-15600?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ekaterina Dimitrova updated CASSANDRA-15600:
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Test and Documentation Plan:
In the cases where the keyspace replication factor is ONE, or if the keyspace
replication factor is equal to the number of racks in the datacenter, the
workload variance drops from ~10 percent to ~6 percent due to algorithmic
optimizations.
Status: Patch Available (was: In Progress)
> Algorithmic token allocation does not handle the racks = RF case well
> ---------------------------------------------------------------------
>
> Key: CASSANDRA-15600
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15600
> Project: Cassandra
> Issue Type: Bug
> Components: Feature/Virtual Nodes
> Reporter: Branimir Lambov
> Assignee: Ekaterina Dimitrova
> Priority: Normal
> Attachments: CASSANDRA-15600 unit.txt, CASSANDRA-15600-jvm.txt.zip,
> Screen Shot 2020-03-02 at 6.55.41 PM.png
>
>
> When the number of racks in a data centre is equal to the replication factor,
> the node allocation algorithm may calculate the target ownership incorrectly
> and allocate unsuitable tokens. This causes some inefficiency when the number
> of nodes in the DC is small, and significant problems if the number of nodes
> in each rack is different.
> In this case (racks count equal to replication factor) the load within each
> rack is effectively distributed independently. The allocation algorithm
> should reflect that, restricting the allocation space to the rack (instead of
> the DC) and using the RF=1 solution.
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