3 min to complete
Scylla replicates data according to a replication strategy that you choose. This strategy will determine the placement of the replicated data. Scylla runs nodes in a hash ring. All nodes are equal: there are no master, slave, or replica sets.
The Replication Factor (RF) is equivalent to the number of nodes where data (rows and partitions) are replicated. Data is replicated to multiple (RF=N) nodes.
An RF of one means there is only one copy of a row in a cluster, and there is no way to recover the data if the node is compromised or goes down. RF=2 means that there are two copies of a row in a cluster. An RF of at least three is used in most systems.
Data is always replicated automatically. Read or write operations can occur to data stored on any of the replicated nodes.
In the example above, our client sends a request to write partition one to node V; one’s data is replicated to nodes W, X, and Z. We have a Replication Factor (RF) of three. In this drawing, V is a coordinator node but not a replicator node. However, replicator nodes can also be coordinator nodes, and often are.
During a read operation, the client sends a request to the coordinator. Effectively because of the RF=3, three nodes respond to the read request.