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From Weijun Li <weiju...@gmail.com>
Subject RackAwareStrategy - add the third datacenter to live cluster with replication factor 3
Date Thu, 11 Feb 2010 19:53:40 GMT
Hello,

I have a testing cluster with: A (dc1), B (dc1), C(dc2), D(dc2). The
replication factor is 2 so I assume each DC will have a complete copy of the
data. Also I'm using PropertyFileEndPointSnitch with rack.properties for the
dc and rack settings.

So, what's the steps to add another datacenter and increase replication
factor to 3 to ensure that dc3 will also get a complete copy of the data?
Meaning each of these 3 dc will have a complete copy of the data and they
keep synchronize with each other with new changes. What I'm guessing is:

1) Increase replication factor of A/B/C/D to 3, modify their rack.properties
to include E(dc3) and F(dc3) then restart them one by one. At this point E
and F haven't been started yet.
2) Bootstrap E and F (both from dc3) to join the cluster.

in this case, will cassandra automatically put the 3rd replica to E and F?

Thanks,
-Weijun

 P.S here what the cassandra document says about dc replication but I'm not
sure what will happen when you join nodes from the 3rd dc.


   -

   RackAwareStrategy: replica 2 is is placed in the first node along the
   ring the belongs in *another* data center than the first; the remaining
   N-2 replicas, if any, are placed on the first nodes along the ring in the
   *same* rack as the first

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