I have a main DC on Microsoft Azure VM and an on-premise DC. Both domain networks are connected with site-to-site VPN.
The purpose of setting up the DC on cloud was to get rid of the old on-premise servers. If the site-to-site VPN is disconnected, there will be login authentication issue. I ended up keeping the old servers up and running.
The on-premise DC stopped working yesterday due to hardware issue. I don't plan to replace the hardware because it is really old already.
Microsoft Azure guarantees at least 99.9% uptime and office Internet has been stable, I am thinking not to replace the old DC. Is it really necessary to have an on-premise DC ?