Question-26: When do you define which replication strategy should be used?

Answer: While creating keyspace, you must define the replica placement strategy and the number of replicas you want to use. 

Question-27: What is the unique feature about the first replica of the data?

Answer: The first replica of data is simply the first copy and it is not unique in any sense. Using the replication strategy, storage engine determines on which node this replica should be placed as well as other remaining replicas.

Question-28: How Cassandra storage engine determines the locations of the nodes, and in which rack or datacenter a new node is placed?

Answer: Using the Snitch, which has mapped IP addresses of the node with the physical or virtual locations. For example, in which rack or datacenter a node is placed. With the help of snitch, which uses the network topology for routing request efficiently on a particular node on a rack in a particular datacenter. 

Question-29: How do you configure a Snitch?

Answer: While creating a cluster you need to configure a Snitch, to propagate the information about the nodes using the gossip protocol, a recommended approach is using the “GossipingPropertyFileSnitch”. 

Question-30: Which all are the main configuration files in Cassandra?

Answer: Below are the main configuration files

• yaml (See below question for more detail)
• options (Java related settings)
• yaml (While using Datastax solution)