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From Jacques-Henri Berthemet <jacques-henri.berthe...@genesys.com>
Subject RE: does c* 3.0 use one ring for all datacenters?
Date Wed, 11 Apr 2018 11:55:16 GMT
Hi,

Each DC has the whole ring, each DC contains a copy of the same data. When you add replication
to a new DC, all data is copied to the new DC.

Within a DC, each range of token is 'owned' by a (primary) node (and replicas if you have
RF > 1). If you add/remove a node in a DC, tokens will be rearranged between all nodes
within the DC only, the other DCs won't be affected.

--
Jacques-Henri Berthemet

-----Original Message-----
From: Jinhua Luo [mailto:luajit.io@gmail.com] 
Sent: Wednesday, April 11, 2018 12:35 PM
To: user@cassandra.apache.org
Subject: does c* 3.0 use one ring for all datacenters?

Hi All,

I know it seems a stupid question, but I am really confused about the documents on the internet
related to this topic, especially it seems that it has different answers for c* with vnodes
or not.

Let's assume the token range is 1-100 for the whole cluster, how does it distributed into
the datacenters? Think that the number of datacenters is dynamic in a cluster, if there is
only one ring, then the token range would change on each node when I add a new datacenter
into the cluster? Then it would involve data migration? It doesn't make sense.

Looking forward to clarification for c* 3.0, thanks!

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