Optimal dedicated servers confgiuration/cluster

Hi all, I write to you hoping to obtain some advices in order to secure our dedicated server infrastructure. I manage a small IT agency that hosts websites and emails for other businesses. Before the OVH blaze we had two dedicated servers one hosted in SBG and the other in GRA. They are in a DNS Cluster and operate as Nameservers for all the domains we host. If something happened to one of the servers we would move the accounts from the damaged one (or the backups from AWS) to the working one. But now we acquired a 3rd server (in Germany) that we intend to keep for emergency and/or backup. So, can you recommend an ideal configuration between our 2 production servers and the third one? Right now we have scheduled backups of all the accounts of the 2 production servers sent to AWS so we can retrieve them from them from the terminal using wget. Is it viable to insert the third server in a cluster and make the accounts of the 2 production servers go there as another form of backup? Is there a way to connect the three servers keeping 2 in production (live) and the third as an emergency option? My idea is something like: something happens to one of the 2 productions servers, we immediately activate the third server and the accounts (that are already there or we send them there via AWS) start propagating with the new IP. Sorry for my poor technical language, If something is not clear I am at your disposal to clarify. Thanks in advance!