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From Alexandru Sicoe <>
Subject replication in a 3 data center setup
Date Mon, 19 Mar 2012 20:50:36 GMT
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?


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