One option for synchronous replication + MySQL is to take a look at DRBD.
Another option is MySQL Cluster, however, there are limitations to be aware of.
Sr Product Marketing Manager
Sun Microsystems, Database Group
> I work for a small business running accounting and business management
> software (SaaS) on a single busy server, and we are planning to
> upscale to multiple servers. Having synchronous data is vital. In
> light of this:
> Is it possible for a replicated server to be synchronous?
> Are slaves run on hardware that is identical to the master?
> Can anybody recommend Continuent's middleware?
> Apologies for cross posting to the replication and cluster lists.
> Many thanks,
> Andrew Martin