All the information in this blog post is subject to change as Exchange Server 2013 is still under construction. Although it’s not very likely that big changes will occur between now an RTM, it might.

The process of creating a Database Availability Group (DAG) in Exchange Server 2013 (Preview) is largely the same as in Exchange Server 2010. You can choose to create a DAG via either the Exchange Administrative Center (GUI) or through the Exchange Management Shell (PowerShell).

I prefer using the Exchange Management Shell over EAC as it provides you more information over the process.

Exchange Management Shell

To configure a Database Availability Group using the EMS, type in the following commands. Replace the example values with the ones that suit your environment:

New-DatabaseAvailabilityGroup –Name DAG01 –WitnessServer SRV01 –WitnessDirectory “C:\FSW” – DatabaseAvailabilityGroupIPAddresses

This command will create the DAG. As part of this process, a computer object, also known as the Cluster Name Object, will automatically be created:


Note   In order for this process to complete successfully, you need to have the appropriate permissions on the container in which the object is created. By default this will be the “Computers”-container. However, it is possible that your Active Directory has been reconfigured to use another container/OU as default location for new computer accounts. Have a look at http://support.microsoft.com/kb/324949 for more information.

Another way to get around the possible issue of permissions, is to create the Cluster Name Object (CNO) upfront. This process is also called “pre-staging”. Doing so will allow you to create the object up-front with another account (that has the appropriate rights) so that you don’t run into any issues when configuring your DAG.

To pre-stage the CNO, complete the following tasks:

  1. Open Active Directory Users & Computers, navigate to the OU in which you want to create the object, right-click and select New > Computer:


  2. Enter a Computer Name and click OKto create the account:


  3. Right-click the new account and select Properties. Open the Security tab and add the following permissions:- Exchange Trusted Subsystem – Full Control
    – First DAG Node (Computer Account) – Full Control

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More information on how to pre-stage the CNO can be found here: http://technet.microsoft.com/en-us/library/ff367878.aspx

Note   if your DAG has multiple nodes across different subnets, you will need to assign an IP address in each subnet to the DAG. To do so, you can separate the IP addresses using a comma:

New-DatabaseAvailabilityGroup –Name DAG01 –WitnessServer SRV01 –WitnessDirectory “C:\FSW” – DatabaseAvailabilityGroupIPAddresses,,

Once the command executed successfully, you can now add mailbox servers to the DAG. You will need to run this command for each server you want to add to the DAG:

Add-DatabaseAvailabilityGroupServer –Identity DAG01 –MailboxServer EX01
Add-DatabaseAvailabilityGroupServer –Identity DAG01 –MailboxServer EX02

Alternatively, you can also add all/multiple mailbox servers at once to the DAG:

Get-MailboxServer | %{Add-DatabaseAvailabilityGroupServer –Identity DAG01 –MailboxServer $_.Name}

Adding Database Copies

Now that your DAG has been created, you can add copies of mailbox databases to other mailbox servers. For example, to add a copy of DB1 to server EX02, you would run the following command:

Add-MailboxDatabaseCopy –Identity DB1 –MailboxServer EX02

Stay tuned! In an upcoming article, I will be talking about configuring high availability for the Client Access infrastructure in Exchange Server 2013 as well as a topic on high availability (more general).

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