Wednesday, April 27, 2016

Configure DAG on Exchange 2016

Exchange 2016 DAG are very similar to Exchange 2013 DAG, however there are some new features.

There are some basic rules for DAG

No shared storage required for Exchange DAG.
All member servers must be in the same AD domain.
16 copies for each database support.
Mailbox server can not be domain controller.
Windows failover cluster is set up when DAG is set up.
Data Center Activation Coordination (DAC)  is configure for site resistance for prevents a split brain syndrome.
DAG is only high availability for the Mailbox servers.

Set up MAPI and Replication Network


First of all we have to add one more network card to configure MAPI & Replication network in your mailbox servers, you can rename the for avoiding the confusion.

We are using 192.168.209.0/24 for MAPI and 172.10.0.0/16 for Replication network.

Next step is to disable the network features that are not require in MAPI adapters, IPv6 should be enabled.

For replication network adapters we need to disable "Client for Microsoft Network" and "File and Printer Sharing for Microsoft networks".

Set the IP address for Replication adapter
next set the DNS tab and uncheck the "Register this connection's addresses in DNS".

Configure Witness Server


You must have an odd number of voters in a cluster. If you have an even number of mailbox servers in the DAG, the DAG will use a node and file share majority quorum model where it will use a file share witness which is created on a witness server during the DAG setup. If you have as odd number of mailbox servers in the DAG then the DAG will use the node majority quorum model and the file share witness will not be used.

As per recommendation  domain controller or DAG member should not be witness server, When we create the DAG, Exchange will create a witness directory and share on the witness server. For this you the " Exchange Trusted Subsystem" AD group is a local administrator on the witness server.
also add the Exchange Trusted Subsystem group as a local administrator on the witness server.

Configure Exchange 2016 Database Availability Group


I will start to use PowerShell to configure DAG, DAG Name is DAG01 and witness Server is my DC (I don't have any option in my lab).

 we can run the following PowerShell command:
New-DatabaseAvailabilityGroup -Name DAG01 -WitnessServer DC.tech.com -FileSystem ReFs

now add the mailbox servers, we do have two mailbox server E16 and E16-1, we can use the below cmdlet :

Add-DatabaseAvailabilityGroupServer -identity DAG01 -mailboxServer E16
Add-DatabaseAvailabilityGroupServer -identity DAG01 -mailboxServer E16-1


After that we can check the status of the DAG with below command:

Get-DatabaseAvailabilitygroup DAG01 -Status


Now you can check the where is our witness server also:

We can verify into witness server also

As you know the Exchange 2016 DAG will configure Network automatically, so now you can check the status of the DAG Network:

You can check some other configuration such as :
Now you check the mailbox database
Now you have to add database one by one on DAG

Now we can check the database copy status:

Testing the DAG


Once configuration complete, i want to check the fail over, so now i have disable one of the my mailbox server MAPI Network card for testing the actual fail over:

Once NIC disabled, checked the Database copy status now

Now we checked the database getting active on another server properly, now i enabled the MAPI network for mailbox server.

Enable Datacenter Activation Coordination Mode


If you have the two site and DAG configure you can use the DAC mode to avoid the split-brain. You can use below command to enable the DAC mode in DAG. you can click here for deep dive for DAC MODE.

Set-DatabaseAvailabilityGroup DAG01 -DatacenterActivationMode DagOnly


In this post we have seen how we can configure the DAG in Exchange 2016, it is same as Exchange 2013 DAG configuration.
Hope this post help you.

Thank you!

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