There are a number of different ways of achieving high availability and scalability with the open source MySQL database. One of those ways is with the Oracle MySQL Cluster solution, which is being updated today to version 7.3.
Tomas Ulin, vice president for MySQL Engineering at Oracle, explained to Database Journal that MySQL server on its own has replication where data can be replicated to one or more read slaves. The model for MySQL Cluster is a bit different.