The only thing you need to be careful about is to have virtual machines with the same hardware specifications which are up to standard with Microsoft requirements. In the case of a virtual setup, you would not need to bother about the underlying infrastructure as this will be catered to by the Hypervisor. This makes the entire difference in the setup as bad or low performing hardware can create issues. In case, something happens to an Active Directory or an Exchange Server, you will not lose internal and external connectivity. Whereas, on the secondary site, you would have the second Exchange Server. On the main site, you will have the Exchange Server and main Active Directory. The design includes a virtual server - VMWare or Hyper-V, depending on your business standard and have the primary site connected with the secondary site. In the scenario of a disaster, it’s obvious that you would not want to keep all your eggs in one basket. It would help in disaster recovery or business continuity program, in case you have an issue with a building. To have a DAG, you must have two separate sites, in different buildings. As the planning of a good infrastructure is the first thing to start with, let’s begin with ‘what would be the ideal setup of an Exchange DAG’.