We have three Windows Server 2012r2 servers which act as a fail-over partner for each other (1 to 1 trust relationship).
This means that the European Server acts as a fail-over partner for the US and Asia, while the US acts as a fail-over partner for Europe. The Asian Server does not act as a fail-over partner as your trust relation is one to one per configured scope. This configuration works fine as leases are replicated between both partners. However we saw that Scope configuration changes are not replicated between the partners unless you initialize a manual replication. We were expecting that the scopes would merge between the partners, however this does not seem to be the case. Yesterday i made several changes to multiple scopes on the European DHCP server. instead of replicating them one by one I choose the "Replicate Scopes" option on the IPV4 level. Today it was reported that many of the configured reservations in the US were gone. The only reasonable explanation is that scope do not merge, but are effectively overwritten with the settings configured in the replication source (the server from where you initiate the replication).
Answers provided are coming from personal experience, and come with no warranty of success. I as everybody else do make mistakes.