Прежде чем создавать DAG через EAC или консоль, нужно подготовить AD
Pre-stage the CNO
Open Active Directory Users and Computers.
Expand the forest node.
Right-click the organizational unit (OU) in which you want to create the new account, select New, and then select Computer.
In New Object — Computer, type the computer account name for the CNO in the Computer name box. This is the name that you’ll use for the DAG. Click OK to create the account.
Right-click the new computer account, and then click Disable Account. Click Yes to confirm the disable action, and then click OK.