Maybe you are talking about sizing, rather than layout but:
Isn't deploying a multiple 2 node dags a good way of making sure that the 2nd server will always have a shadow copy of mails in...
John Savill's PowerShell Master Class
Join John Savill for 9 hours of comprehensive PowerShell training. This course will start from the ground up, walking through the basics of PowerShell, how to create basic scripts, and building toward creating custom modules to achieve amazing results in your environment, in non-Microsoft environments, and in Azure.