I have a load balancer and several servers behind it. I'm looking for a multi master file replication tool that would allow me to write on any of the machines and replicate the content on all the others, on an event-basis, in a very small timeframe (5 sec).

A single NFS volume mounted on all servers will not suffice, because it becomes a single point of failure.

I'm running CentOS on the servers, the load balancer has proprietary software.