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From Vijay <vijay2...@gmail.com>
Subject Re: Docs: Token Selection
Date Wed, 15 Jun 2011 18:10:28 GMT
The problem in the above approach is you have 2 nodes between 12 to 4 in DC1
but from 4 to 12  you just have 1.... (Which will cause uneven distribution
of data the node)
It is easier to think of the DCs as ring and split equally and interleave
them together....

DC1 Node 1 : token 0
DC1 Node 2 : token 8..

DC2 Node 1 : token 4..
DC2 Node 1 : token 12..

Regards,
</VJ>



On Tue, Jun 14, 2011 at 7:31 PM, AJ <aj@dude.podzone.net> wrote:

>  Yes, which means that the ranges overlap each other.
>
> Is this just a convention, or is it technically required when using
> NetworkTopologyStrategy?  Would it be acceptable to split the ranges into
> quarters by ignoring the data centers, such as:
>
> DC1
> node 1 = 0      Range: (12, 16], (0, 0]
> node 2 = 4      Range: (0, 4]
>
> DC2
> node 3 = 8      Range: (4, 8]
> node 4 = 12   Range: (8, 12]
>
> If this is OK, are there any drawbacks to this?
>
>
>
> On 6/14/2011 6:10 PM, Vijay wrote:
>
> Yes... Thats right...  If you are trying to say the below...
>
>  DC1
>  Node1 Owns 50%
>
>  (Ranges 8..4 -> 8..5 & 8..5 -> 0)
>
> Node2 Owns 50%
>
> (Ranges 0 -> 1 & 1 -> 8..4)
>
>
>  DC2
>  Node1 Owns 50%
>
>  (Ranges 8..5 -> 0 & 0 -> 1)
>
>   Node2 Owns 50%
>
>   (Ranges 1 -> 8..4 & 8..4 -> 8..5)
>
>
>  Regards,
> </VJ>
>
>
>
> On Tue, Jun 14, 2011 at 3:47 PM, AJ <aj@dude.podzone.net> wrote:
>
>> This http://wiki.apache.org/cassandra/Operations#Token_selection  says:
>>
>> "With NetworkTopologyStrategy, you should calculate the tokens the nodes
>> in each DC independantly."
>>
>> and gives the example:
>>
>> DC1
>> node 1 = 0
>> node 2 = 85070591730234615865843651857942052864
>>
>> DC2
>> node 3 = 1
>> node 4 = 85070591730234615865843651857942052865
>>
>>
>> So, according to the above, the token ranges would be (abbreviated nums):
>>
>> DC1
>> node 1 = 0      Range: (8..4, 16], (0, 0]
>> node 2 = 8..4   Range: (0, 8..4]
>>
>> DC2
>> node 3 = 1      Range: (8..5, 16], (0, 1]
>> node 4 = 8..5   Range: (1, 8..5]
>>
>>
>> If the above is correct, then I would be surprised as this paragraph is
>> the only place were one would discover this and may be easy to miss...
>> unless there's a doc buried somewhere in plain view that I missed.
>>
>> So, have I interpreted this paragraph correctly?  Was this design to help
>> keep data somewhat localized if that was important, such as a geographically
>> dispersed DC?
>>
>> Thanks!
>>
>
>
>

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