The basic steps to creating a DAG of course means having Exchange servers setup prior with their respective databases.
The core components to pre-stage for a DAG are:
1. Designate a Witness Server – In production, best practice suggests in a separate location than that of your DAG(s).
2. Database Availability Group Name
3. Witness Directory
4. Database Availability Group IP address
5. Cluster Name Object
Start by creating a witness server for your DAG.
To pre-stage the witness server you create a folder on the C: drive of the witness server. On my server I call it “ExchangeFWS” so that the witness server has a spot to store its logs, and I can logically identify it later.
Then you will need to add the Exchange Trusted Subsystem to the local administrators group of the witness server.
Follow this by going to your domain controller and creating a computer object (I give mine the same name as the DAG, in my case: DAG01.) This will be the CNO.
While still in Active Directory Users and Computers, enable Advanced Features under the view drop down menu and navigate back to the location of my the DAG01 computer object.
Right click the object and select properties and navigate to to the security tab.
Once here, add the exchange servers computer objects with full permissions.
Exit out of the properties window and right click your DAG computer object and disable it. This is done for security so that you don’t have an unused computer object hanging out in your active directory.
And that’s it!
Now you can get ready to create your DAG.