Replication Overview

The basic problem replication solves is keeping one server’s data synchronized with another’s. Many replicas can connect to a single master and stay in sync with it, and a replica can, in turn, act as a master. You can arrange masters and replicas in many different ways.

MySQL supports two kinds of replication: statement-based replication and row-based replication. Statement-based (or “logical”) replication has been available since MySQL 3.23. Row-based replication was added in MySQL 5.1. Both kinds work by recording changes in the master’s binary log^[145] and replaying the log on the replica, and both are asynchronous—that is, the replica’s copy of the data isn’t guaranteed to be up-to-date at any given instant. There are no guarantees as to how large the latency on the replica might be. Large queries can make the replica fall seconds, minutes, or even hours behind the master.