How many PE Relay servers can store box ssb have? We want to build a two relay per dmz solution that forwards logs to Splunk.

Hi, I would like to ask you guys, how many PE server Relays can store box hold and have no issue with licensing? We are building a fail safe solution and want to have two PE relay servers with a load balancer and forward the logs depending on availability and then to Splunk via heavy forwarder. So, anyone could confirm from their experience if there is any issues with having more PE relay servers. Otherwise if someone know how to make a cluster solution would love to hear that too.