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From "Mullen, Robert" <robert.mul...@pearson.com>
Subject Re: Clarification on how multi-DC replication works
Date Tue, 11 Feb 2014 17:36:08 GMT
So is that picture incorrect, or just incomplete missing the piece on how
the nodes reply to the coordinator node.


On Tue, Feb 11, 2014 at 9:38 AM, sankalp kohli <kohlisankalp@gmail.com>wrote:

> @Mullen,
> I think your diagram does not answer the question on responses.
> @Sameer
> 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 <robert.mullen@pearson.com
> > wrote:
>
>> 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 <sameer@blueplastic.com>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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