Galera implements wsrep pluggable interface, as defined in project: https://launchpad.net/wsrep and can provide several replication modes and topologies, including the ultimate Synchronous Multi-Master replication.

There are currently two MySQL based DBMS projects providing wsrep API, and thus implementing tightly coupled Galera clustering solution:

https://launchpad.net/codership-mysql project implements MySQL 5.* based MySQL/Galera cluster.

https://launchpad.net/codership-maria project implements MariaDB 5.* based MariaDB/Galera cluster.

Main discussion happens here: http://groups.google.com/group/codership-team?hl=en

* * * Building on CentOS/RHEL 5.x: * * *
CentOS/RHEL by default uses a very old version of GCC and a likewise ancient version of BOOST that lacks important features. In order to build Galera on CentOS/RHEL one needs to:
 1) Install gcc44 and gcc44-c++ packages and set CC and CXX variables accordingly:
    # yum install gcc44 gcc44-c++
    # export CC=gcc44
    # export CXX=g++44
 2) Remove standard boost and boost-devel packages (if present)
 3) Install boost141-devel package:
    # yum install boost141-devel
 4) Make link from /usr/include/boost to /usr/include/boost141:
    # cd /usr/include
    # ln -sf boost141/boost boost
Once again big thanks to Red Hat for traditionally providing us with the most adequate development platform since 1996.