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From aaron morton <aa...@thelastpickle.com>
Subject Re: replication in a 3 data center setup
Date Tue, 20 Mar 2012 17:17:49 GMT
> More exactly, if you write a record in a node in DC1 will it send one replica of it to
DC2 and then another replica to DC3? Or will the node in DC2 replicate the record to DC3 in
a chain effect?
Coordinator in DC 1 will send the mutation to both DC2 and DC3 at the same time. 

> I need to understand this because the connection between DC1 and DC2/DC3 is limited and
ideally I would only want to send a replica to DC2 and have DC2 send a replicat to DC3. Is
this possible?
No. That would tie the availability if DC 3 directly to DC 2. 

Cheers

-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 20/03/2012, at 9:50 AM, Alexandru Sicoe wrote:

> Hi everyone,
> 
> If you have 3 data centers (DC1,DC2 and DC3) with 3 nodes each and you have a keyspace
where the strategy options are such that each DC gets 2 replicas. If you only write to the
nodes in DC1 what is the path the replicas take? Assuming you've correctly interleaved the
tokens of all the nodes [(DC1: x,y,z), (DC2:x+1,y+1,z+1), (DC3:x+2,y+2,z+2)]? 
> 
> More exactly, if you write a record in a node in DC1 will it send one replica of it to
DC2 and then another replica to DC3? Or will the node in DC2 replicate the record to DC3 in
a chain effect?
> 
> I understand that each DC handles it's own internal replication (after a node receives
one replica).
> 
> I need to understand this because the connection between DC1 and DC2/DC3 is limited and
ideally I would only want to send a replica to DC2 and have DC2 send a replicat to DC3. Is
this possible?
> 
> Cheers,
> Alex


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