Hi,these advice are very welcome.

@Dane, about the rack awareness, we use only one rack per DC, so I guess using EC2MultiRegionSnitch will do just fine and it doesn't need any configuration. Does it seem right to you. If we are someday interested on multi racks I will make sure to use them properly. Thank you for this insight anyway. You are advising me to test it, what would be a good way of testing it (I can use AWS EC2 instances if needed) ?

@Aaron

"I recommend using the same number of nodes in both DC's."

Why ? I mean we have maybe only 5% of our customers on the us-east zone, what in C* require to have the same number of node on each DC ?

"Add the nodes (I recommend 6) with auto_bootstrap: false added to the yaml.
update the keyspace replication strategy to add rf:3 for the new DC. 
Use nodetool rebuild on the new nodes to rebuild them from the us-west DC. "

What is better on adding nodes with no data and then rebuild them compared to using the auto_bootstrap ?

"I prefer to use the offset method. Take the 6 tokens from your us-west DC and add 100 to them for the new dc. "

Any doc on this ? I am not aware of all the possibilities. Why is this the best method according to you ?

About seeds => "Yes. Have 3 from each."

What is the point of this ?

I didn't thought this change would be that tricky, thank you guys for these warnings and your help ;)

Alain


2013/4/23 Dane Miller <dane@optimalsocial.com>
On Thu, Apr 18, 2013 at 7:41 AM, Alain RODRIGUEZ <arodrime@gmail.com> wrote:
> I am wondering about the process to grow from one data center to a few of
> them. First thing is we use EC2Snitch for now. So I guess we have to switch
> to Ec2MultiRegionSnitch.
>
> c/ I am using the SimpleStrategy. Is it worth it/mandatory to change this
> strategy when using multiple DC ?

I suggest you thoroughly read the datastax documentation on cassandra
replication.  The change you are planning is big - make sure to try it
in a test environment first.  Also, you might find you don't really
need Cassandra's rack aware feature, and can operate using
(Gossiping)PropertyFileSnitch.  The rack feature is listed as an
"anti-pattern" here:
http://www.datastax.com/docs/1.2/cluster_architecture/anti_patterns

Here are some recent discussions on this list:
http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/migrating-from-SimpleStrategy-to-NetworkTopologyStrategy-tp7586272.html
http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/migrating-from-SimpleStrategy-to-NetworkTopologyStrategy-tp7481090.html

Dane