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, 
 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.


> 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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