Cassandra Cluster Vs Nodes

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I am beginner in Cassandra, I am trying to understand few basic things.

1) Cassandra Cluster : Does it mean a physical server? Is it possible to run multiple clusters on a single physical machine?

2) Cassandra Nodes : By definition it looks that one cluster can have multiple nodes. Can we have multiple nodes on a single physical machine? or one node means one single machine?

3) I have two physical machines and I just installed Cassandra server on both machines and configured syncing between the both Cassandra servers, so if I create any keyspace with NetworkTopologyStrategy I am able to see on both servers. Does it mean that I created two clusters or two nodes?

Need help on above questions.

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cassandra

1 Answers

1
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Let us work with JVM as a unit.

Cassandra Node: It is a single JVM instance to run Cassandra. It can be run on a single physical machine or on a VM or docker container.

Cassandra Cluster: One or more group of Cassandra nodes form a Cassandra cluster.

So if you have 2 physical machines you can always run more than 2 nodes depending on the capacity of your machine. You can also run multiple clusters. i.e eg: you can create 6 VM to prepare 6 nodes and group them into two clusters with 3 each. This is controlled by cassandra.yaml.

Does it mean that I created two clusters or two nodes? No, it means you created two nodes and grouped them into one cluster.