Working with replication systems is not easy. Learning and testing different kind of MySQL replications and fine-tuning it to your specific needs is a time-consuming endeavor. Also you need to have several MySQL servers at your disposal. To overcome these limitations, Stardata created a MySQL 5 Replication Playground, a painless installation of 4 replicating nodes in one server, using MySQL 5.

Replication Playground creates four nodes in either standard or circular replication, using MySQL 5.0 or 5.1 tables. It will install four nodes under your home directory, and it will provide some useful commands to start, use and stop each node. With this package you can play with replication all you want.

You can download it here.

BTW: Did you know that you can actually create Master-Master replication (with mutual master-slave relationship) with MySQL 5.1 database with failover, a solution which is much cheaper than MySQL clustering which is memory bound. So now you can make changes to both the database simultaneously. However don't forget to configure the automatic id generator parameters. You can use up to 10 servers without appreciable performance impact.