Replication provides fault tolerance:

• Replication Factor (RF): Number of copies of each piece of data
• Replication Strategy: Determines which nodes get replicas
  • SimpleStrategy: For single datacenter
  • NetworkTopologyStrategy: For multiple datacenters
• Coordinator Node: Any node can coordinate a request
• Replica Nodes: Nodes that store copies of the data

Example: RF=3 means each piece of data is stored on 3 different nodes.