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From "Dikang Gu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-12777) Optimize the vnode allocation for single replica per DC
Date Mon, 17 Oct 2016 20:09:58 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-12777?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15583301#comment-15583301
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Dikang Gu commented on CASSANDRA-12777:
---------------------------------------

Sure, I add the limit of the range of take over ratio, for both MIN and MAX ratios. Here is
the updated patch, https://github.com/DikangGu/cassandra/commit/5e837747974b5faa9833dc55ac5bd33a8c5e8b31,
and the simulation results are here, https://gist.github.com/DikangGu/29a6b5ab876ff6979de45118b855622b.
I'd like to go with 0.90, since it produces better results.

Thanks.

> Optimize the vnode allocation for single replica per DC
> -------------------------------------------------------
>
>                 Key: CASSANDRA-12777
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-12777
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Dikang Gu
>            Assignee: Dikang Gu
>             Fix For: 3.x
>
>
> The new vnode allocation algorithm introduced in CASSANDRA-7032 is optimized for the
situation that there are multiple replicas per DC.
> In our production environment, most cluster only has one replica, in this case, the algorithm
does not work perfectly. It always tries to split token ranges by half, so that the ownership
of "min" node could go as low as ~60% compared to avg.
> So for single replica case, I'm working on a new algorithm, which is based on Branimir's
previous commit, to split token ranges by "some" percentage, instead of always by half. In
this way, we can get a very small variation of the ownership among different nodes.



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