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From Jinhua Luo <luajit...@gmail.com>
Subject Re: does c* 3.0 use one ring for all datacenters?
Date Wed, 11 Apr 2018 12:26:16 GMT
Thanks for your reply. I also think separate rings are more reasonable.

So one ring for one dc is only for c* 1.x or 2.x without vnode?

Check these references:

https://docs.datastax.com/en/archived/cassandra/1.1/docs/initialize/token_generation.html
http://www.luketillman.com/one-token-ring-to-rule-them-all/
https://community.apigee.com/articles/13096/cassandra-token-distribution.html

Even the riak official said c* splits the ring across dc:
http://basho.com/posts/business/riak-vs-cassandra-an-updated-brief-comparison/

Why they said each dc has its own ring?


2018-04-11 19:55 GMT+08:00 Jacques-Henri Berthemet
<jacques-henri.berthemet@genesys.com>:
> 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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