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From Jeremiah Jordan <>
Subject Re: Rationale behind incrementing all tokens by one in a different datacenter (was: running two rings on the same subnet)
Date Mon, 05 Mar 2012 16:05:33 GMT
There is a requirement that all nodes have a unique token.  There is 
still one global cluster/ring that each node needs to be unique on.  The 
logically seperate rings that NetworkTopologyStrategy puts them into is 
hidden from the rest of the code.


On 03/05/2012 05:13 AM, Hontvári József Levente wrote:
> I am thinking about the frequent example:
> dc1 - node1: 0
> dc1 - node2: large...number
> dc2 - node1: 1
> dc2 - node2: large...number + 1
> In theory using the same tokens in dc2 as in dc1 does not 
> significantly affect key distribution, specifically the two keys on 
> the border will move to the next one, but that is not much. However it 
> seems that there is an unexplained requirement (at least I could not 
> find an explanation), that all nodes must have a unique token, even if 
> they are put into a different circle by NetworkTopologyStrategy.
> On 2012.03.05. 11:48, aaron morton wrote:
>> Moreover all tokens must be unique (even across datacenters), 
>> although - from pure curiosity - I wonder what is the rationale 
>> behind this.
> Otherwise data is not evenly distributed.

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