plan to switch fro SimpleStrategy to NetworkTopologyStrategy

[Igor <ig...@4friends.od.ua>]

Hi,

This is my first post, so first of all - thanks to Cassandra authors and 
community for their excellent job!

Now to my question... I need a plan for transition from SimpleStrategy 
to NetworkSopologyStrategy (as I have to add two servers from remote 
datacenter with RTT up to 120ms to my cluster).

Cluster consists from 10 nodes in 5 datacenters (2 node per DC), each 
node carry about 4G of data in keyspace

Keyspace: meter:
   Replication Strategy: org.apache.cassandra.locator.SimpleStrategy
   Durable Writes: true
     Options: [replication_factor:3]

Originally I planned (and tested) simply rolling restart nodes with 
NetworkTopologyStategy enabled in cassandra.yaml (and proper 
cassandra-topology.properties file in place) and after nodes restarted - 
update my keyspace with option {DC1:1,DC2:1,...}. But my concern is - 
will cassandra begin to move data location right after restart with 
enabled NTS (and should I wait for it during rolling restart?) or only 
after keyspace update with new options?

Or there is some other way?

Thanks!