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From Sasha Dolgy <>
Subject Re: Docs: Token Selection
Date Fri, 17 Jun 2011 19:27:50 GMT
Replication factor is defined per keyspace if i'm not mistaken.  Can't
remember if NTS is per keyspace or per cluster ... if it's per
keyspace, that would be a way around it ... without having to maintain
multiple clusters .... just have multiple keyspaces ...

On Fri, Jun 17, 2011 at 9:23 PM, AJ <> wrote:
> On 6/17/2011 12:32 PM, Jeremiah Jordan wrote:
>>        Run two clusters, one which has {DC1:2, DC2:1} and one which is
>> {DC1:1,DC2:2}.  You can't have both in the same cluster, otherwise it
>> isn't possible to tell where the data got written when you want to read
>> it.  For a given key "XYZ" you must be able to compute which nodes it is
>> stored on just using "XYZ", so a strategy where it is on nodes
>> DC1_1,DC1_2, and DC2_1 when a node in DC1 is the coordinator, and to
>> DC1_1, DC2_1 and DC2_2 when a node in DC2 is the coordinator won't work.
>> Given just "XYZ" I don't know where to look for the data.
>>        But, from the way you describe what you want to happen, clients
>> from DC1 aren't using data inserted by clients from DC2, so you should
>> just make two different Cassandra clusters.  Once for the DC1 guys which
>> is {DC1:2, DC2:1} and one for the DC2 guys which is {DC1:1,DC2:2}.
> Interesting.  Thx.

Sasha Dolgy

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