Additonal question: doesn't a classical single-master + multiple slaves scenarios, where each slave use chain overlay to automatically forward all changes to the master, also achieve exactly what is described in the mirror mode description ?
No. Because if the master dies in the single-master scenario, there is no new master to take over. With mirror mode, which is supposed to include a heart-beat monitor and a load balancer, allows the mirror master to take over if the other one fails.
--Quanah -- Quanah Gibson-Mount Principal Software Engineer Zimbra, Inc -------------------- Zimbra :: the leader in open source messaging and collaboration