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From Tyler Hobbs <ty...@datastax.com>
Subject Re: Expanding cluster to include a new DR datacenter
Date Thu, 23 Aug 2012 02:10:10 GMT
If you didn't see this particular section, you may find it useful:
http://www.datastax.com/docs/1.1/operations/cluster_management#adding-a-data-center-to-a-cluster

Some comments inline:

On Wed, Aug 22, 2012 at 3:43 PM, Bryce Godfrey <Bryce.Godfrey@azaleos.com>wrote:

>  We are in the process of building out a new DR system in another Data
> Center, and we want to mirror our Cassandra environment to that DR.  I have
> a couple questions on the best way to do this after reading the
> documentation on the Datastax website.  We didn’t initially plan for this
> to be a DR setup when first deployed a while ago due to budgeting, but now
> we need to.  So I’m just trying to nail down the order of doing this as
> well as any potential issues.****
>
> ** **
>
> For the nodes, we don’t plan on querying the servers in this DR until we
> fail over to this data center.   We are going to have 5 similar nodes in
> the DR, should I join them into the ring at token+1?
>

Join them at token+10 just to leave a little space.  Make sure you're using
LOCAL_QUORUM for your queries instead of regular QUORUM.


> ****
>
> ** **
>
> All keyspaces are set to the replication strategy of SimpleStrategy.  Can
> I change the replication strategy after joining the new nodes in the DR to
> NetworkTopologyStategy with the updated replication factor for each dr?
>

Switch your keyspaces over to NetworkTopologyStrategy before adding the new
nodes.  For the strategy options, just list the first dc until the second
is up (e.g. {main_dc: 3}).


> ****
>
> ** **
>
> Lastly, is changing snitch from default of SimpleSnitch to
> RackInferringSnitch going to cause any issues?  Since its in the
> Cassandra.yaml file I assume a rolling restart to pick up the value would
> be ok?
>

This is the first thing you'll want to do.  Unless your node IPs would
naturally put all nodes in a DC in the same rack, I recommend using
PropertyFileSnitch, explicitly using the same rack.  (I tend to prefer
PFSnitch regardless; it's harder to accidentally mess up.)  A rolling
restart is required to pick up the change.  Make sure to fill out
cassandra-topology.properties first if using PFSnitch.


> ****
>
> ** **
>
> This is all on Cassandra 1.1.4, Thanks for any help!****
>
> ** **
>
> ** **
>



-- 
Tyler Hobbs
DataStax <http://datastax.com/>

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