What is meant by a node in cassandra?

Question

I am new to Cassandra and I want to install it. So far I've read a small article on it.

But there one thing that I do not understand and it is the meaning of 'node'.

Can anyone tell me what a 'node' is, what it is for, and how many nodes we can have in one cluster ?

Answer 1

A node is the storage layer within a server.

Newer versions of Cassandra use virtual nodes, or vnodes. There are 256 vnodes per server by default.

A vnode is essentially the storage layer.

• machine: a physical server, EC2 instance, etc.
• server: an installation of Cassandra. Each machine has one installation of Cassandra. The Cassandra server runs core processes such as the snitch, the partitioner, etc.
• vnode: The storage layer in a Cassandra server. There are 256 vnodes per server by default.

Helpful tip:

Where you will get confused is that Cassandra terminology (in older blog posts, YouTube videos, and so on) had been used inconsistently. In older versions of Cassandra, each machine had one Cassandra server installed, and each server contained one node. Due to the 1-to-1-to-1 relationship between machine-server-node in old versions of Cassandra people previously used the terms machine, server and node interchangeably.