I would go with option 1. 

I think it is the safer of the two options, involves less work and if something were to go wrong mid migration you can remove the second DC from your keyspace replication and have a clean break. SimpleStrategy will work across DCs. It is generally advised to not use it across DCs as it is hard to maintain and can induce latency on writes depending on DC distance, however as you are just migrating and then killing the original DC you won't face these issues.


On Mon, Apr 7, 2014 at 5:25 PM, Brandon McCauslin <bm3780@gmail.com> wrote:
We're currently running a small 5 node 2.0.5 cluster in a single datacenter using the SimpleStrategy replication strategy with replication factor of 3.  We want to migrate our data from our current datacenter to a new datacenter, without incurring any downtime or data loss.  There is no plan to maintain or keep the old (current) datacenter after the migration is complete.  I'm wondering how best to go about this migration.

Shoud We:
  1. add a 2nd datacenter as described here - "Adding a datacenter to cluster", then decommission the 1st datacenter.  Can we even do this given we're currently setup with SimpleStrategy replication?
  2. or should we just start adding new nodes from the new datacenter to our existing cluster as described here?  Then once we've added all the new nodes, start decommissioning all the old nodes from the old/current datacenter as described here.
Thanks for your help and time!