MySQL Cluster as back-end for FreeRadius

Newbie question. Has someone successfully configured a high-availability MySQL cluster as a back-end for FreeRadius? Trying to find out what architecture was used to achieve the cluster or high availabilty and how successful you have been in a Production Environment. 1. Master/Master Replication? 2. Master/Slave Replication (for DR)? 3. MySQL Cluster using NDB? What other backend databases in a high avilable configureation have been used/tested. Thanks.