Can we set up a Disaster Recovery environment with lesser nodes Cassandra Cluster?

[#1]

Can we set up a Disaster Recovery environment with lesser nodes Cassandra Cluster. we have 3 nodes Cassandra Cluster and planning to set up a 2 nodes Cassndra Cluster in Disaster Environment, can we replicate the Prod env 3 nodes Cassandra Cluster in 3 nodes DR Cassandra cluster.

Please help us in understanding the feasibility and challenges to go ahead with this approach

[bkrishnankutty]

IF you are looking for an Active DR, you need a minimum of 3 node C* cluster with Replication Factor of 3 in the DR region.

[#3]

First of all is it feasible to replicate 3 nodes C* cluster to 2 nodes C* cluster?

We are ok to sacrifice performance but DR environment should be up and running for a day or so,even than can't we manage with 2 node C* cluster.

Just for understanding can we replicate 3 nodes Cassandra Cluster into 2 nodes Cassandra cluster, if yes can we replicate vise versa from 2 nodes C* cluster to 3 nodes C* cluster.

[cmbrown]

@satish chandra j as baba pointed out to you in our Edge configuration a minimum of three is required as we use Quorum and RF=3, this avoids a single node failure causing a system failure. You can try out some of your scenarios you are asking with this : https://www.ecyrd.com/cassandracalculator/ which can give you the details around failure potential in your DR environment.

[bkrishnankutty]

To have a functional DR you need 3 replica nodes, which is a minimum number of C* node required. Refer to the consistency level of Cassandra.

https://docs.datastax.com/en/cassandra/2.1/cassandra/dml/dmlClientRequestsRead.html

To answer your question, Yes, its possible to have C* replicated to a 2nd region with Replication Factor of 1. Then you are essentially looking for a copy of data as a backup in alternate region. Not a practical DR.

Apigee do NOT reccomend to use a C* configuration less than 3 nodes and RF=3.