Their primary location, here in xxxx, has a new server up and running with a single Windows Server 2012 R2 Standard VM that is acting as their domain controller, primary DNS server, and file server for their xxxxx office. In xxxxx, we have an identical server that we are spinning up a new Windows Server 2012 R2 Standard VM on. This server will act as a file server for their aaaaaa office, but I also want it to be a domain controller and DNS server for their office. Now, here's the thing though. I want them to BOTH be on the same domain. In other words, I want to setup xxxxxx to be the primary domain controller, and aaaaaa as the secondary domain controller. All of the workstations will point to the xxxx VM as their primary DNS and the aaaaa VM as their secondary DNS via a site-to-site VPN connecting the two networks. In aaaaa, it would be just the reverse, with their workstations looking at the aaaaa VM as their primary DNS and then xxxxx as the secondary DNS.
In practice, this was working fine when we had it setup working in the lab. However, from an actual deployment and production standpoint, what do you think? Are there issues with having basically a "child" domain controller of a primary domain located in a different location connected via Site-to-Site VPN?