Exchange Server 2016 – Creating a DAG

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Creating a DAG object in an Exchange Server 2016 organization and preparing the witness server to support the new DAG.


The DAG is a logical object created in the Exchange Server organization, and after its creation the administrator can start adding servers, and finally mailboxes to start the replication process. Any Exchange high available solution requires a DAG, and that is the first step to create it.

A DAG requires a Witness Server and we will be using the local file server called MTLFS01.



Preparing the Witness Server…

Logged on the Witness Server, our first step is to install the required Windows Feature to support the Witness Shared Folder, and we can do that using the following cmdlet.

Add-WindowsFeature File-Services,FS-FileServer


The second step is to open the Computer Management, and add the group Exchange Trusted Subsystem as administrator of that server. If your local administrators are managed through GPO, then you have to make sure that group is part of that GPO.


Configuring the DAG…

After having the network adapters configured, open Exchange Admin Center, click on Servers (1), and then on Database Availability Groups (2), click on Add (3)


In the new page, define a name for the new Database Availability Group, we will use AP, and specify the server name or FQDN of the witness server, and finally to create a DAG without an IP associated at the cluster level, we can use non-AAP (Administrative Access Point) by using It helps to keep things simple. Click on Save.


The result will be a new entry on the Database availability groups page containing all the information that we provided in the previous wizard. The current DAG is just a logical object and it does not have servers associated to it at this point.


Validating the DAG creation process…

All DAG processes will log their information under C:\ExchangeSetupLogs\DAGTasks as shown in the image below. In case of encountering an error, the administrator always can check those log files to identify the issue before repeating the operation.


In this Tutorial we went over the process to prepare the witness server and to create the DAG, in the next Tutorials here at we will be managing servers in our DAG and replicating Databases.

Written by Anderson Patricio

Anderson Patricio is a Canadian Exchange Server MVP and MCSM (Solutions Master) and he contributes to the Microsoft Community with articles, tutorials, blog posts, forums and book reviews. He is a regular contributor at, and (Portuguese).