One in a different city. These are individual servers, pretty much works as file servers. We upload images to those servers and at the end of the month we send the images to our clients (Digitalization services).
We have Darkfiber between sites so we can reach the LAN from any city. What I need to do is find a way to make HA/contigency/Fail over. It means that if users in site C their server fails. They can use Site B or A to upload files. If site A server fails they can use Site B or C Server to upload files.
Keep in mind is not a cluster of servers but individual servers and everything is for internal use. Internet access is not required.