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Here is my use case: I have a single DC Cassandra cluster(3 nodes) with RF 2. This Cluster is running on my on-premises DC. Here is my question, I am hoping to add 3 EC2 nodes into this cluster and then change the RF to say 4, also add one of the ec2 nodes as a seed after all 3 nodes fully join the cluster.

Do I need to change the Snitch on the EC2 nodes? or can I just add each nodes?

If you have implemented this use case, I will appreciate a clean clear step and what gotcha I should look out for?

mic255
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  • when you say RF:4 dont you mean DC-on-premise:2 and DC-aws:2 ? What snitch do you already have? – markc Sep 13 '18 at 12:21
  • @markc. my current snitch is SimpleSnitch. which is what I have running on my on-premise Cassandra cluster. As for RF this is what I have CREATE KEYSPACE *** WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 2} so, I am hoping after all the ec2 nodes are added, I can then change it to CREATE KEYSPACE **** WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 4} Let me know if my idea makes sense. feel free to ping me any documentation that you have. Thanks – mic255 Sep 13 '18 at 13:40
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    ok so `SimpleSnitch` (which is the default) is going to cause you a problem here. Its probably best to use the `GossipingPropertyFileSnitch` instead – markc Sep 13 '18 at 14:18
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    One you have switched out the snitch then change the KS replication to use `NetworkTopologyStrategy` – markc Sep 13 '18 at 14:19

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You can add 3 EC2 nodes to your on-prem cluster, but... you will have to set up 2 data centers to do it with 3 nodes in each DC, 2 DCs in your cluster. You won't be able to use SimpleSnitch; as markc commented, your best bet is GossipingPropertyFileSnitch. Although you didn't mention it, SimpleStrategy is not recommended for production and you'll need to change it to NetworkTopologyStrategy. Markc should post his comments as the answer here :)

LHWizard
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