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From sankalp kohli <>
Subject Re: Clarification on how multi-DC replication works
Date Tue, 11 Feb 2014 16:38:01 GMT
I think your diagram does not answer the question on responses.
All nodes in DC2 will replay back to the co-ordinator in DC1. So if you
have replication of DC1:3,DC2:3. A co-ordinator node will get 6 responses
back if it is not in the replica set.
Hope that answers your question.

On Tue, Feb 11, 2014 at 8:16 AM, Mullen, Robert

> I had the same question a while back and put together this picture to help
> me understand the flow of data for multi region deployments. Hope that it
> helps.
> On Mon, Feb 10, 2014 at 7:52 PM, Sameer Farooqui <>wrote:
>> Hi,
>> I was hoping someone could clarify a point about multi-DC replication.
>> Let's say I have 2 data centers configured with replication factor = 3 in
>> each DC.
>> My client app is sitting in DC 1 and is able to intelligently pick a
>> coordinator that will also be a replica partner.
>> So the client app sends a write with consistency for DC1 = Q and
>> consistency for DC2 = Q to a coordinator node in DC1.
>> That coordinator in DC1 forwards the write to 2 other nodes in DC1 and a
>> coordinator in DC2.
>> Is it correct that all 3 nodes in DC2 will respond back to the original
>> coordinator in DC1? Or will the DC2 nodes respond back to the DC2
>> coordinator?
>> Let's say one of the replica nodes in DC2 is down. Who will hold the hint
>> for that node? The original coordinator in DC1 or the coordinator in DC2?

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