cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Sasha Dolgy <sdo...@gmail.com>
Subject Re: Docs: Token Selection
Date Thu, 16 Jun 2011 15:11:49 GMT
So, with ec2 ... 3 regions (DC's), each one is +1 from another....?
On Jun 16, 2011 3:40 PM, "AJ" <aj@dude.podzone.net> wrote:
> Thanks Eric! I've finally got it! I feel like I've just been initiated
> or something by discovering this "secret". I kid!
>
> But, I'm thinking about using OldNetworkTopStrat. Do you, or anyone
> else, know if the same rules for token assignment applies to ONTS?
>
>
> On 6/16/2011 7:21 AM, Eric tamme wrote:
>> AJ,
>>
>> sorry I seemed to miss the original email on this thread. As Aaron
>> said, when computing tokens for multiple data centers, you should
>> compute them independently for each data center - as if it were its
>> own Cassandra cluster.
>>
>> You can have "overlapping" token ranges between multiple data centers,
>> but no two nodes can have the same token, so for subsequent data
>> centers I just increment the tokens.
>>
>> For two data centers with two nodes each using RandomPartitioner
>> calculate the tokens for the first DC normally, but int he second data
>> center, increment the tokens by one.
>>
>> In DC 1
>> node 1 = 0
>> node 2 = 85070591730234615865843651857942052864
>>
>> In DC 2
>> node 1 = 1
>> node 2 = 85070591730234615865843651857942052865
>>
>> For RowMutations this will give each data center a local set of nodes
>> that it can write to for complete coverage of the entire token space.
>> If you are using NetworkTopologyStrategy for replication, it will give
>> an offset mirror replication between the two data centers so that your
>> replicas will not get pinned to a node in the remote DC. There are
>> other ways to select the tokens, but the increment method is the
>> simplest to manage and continue to grow with.
>>
>> Hope that helps.
>>
>> -Eric
>>
>

Mime
View raw message