http://axis.apache.org/axis2/java/core/docs/clustering-guide.html is obsolete! I just came across this after a user asked a related question on the synapse-user list. I will try to find some time to update it. In the mean time, the following articles can be used as a reference, if required.
http://wso2.org/library/articles/introduction-wso2-carbon-clustering http://wso2.org/library/articles/wso2-carbon-cluster-configuration-language
