Database Availability Groups(DAGs) in Exchange 2010 is a Data Redundant, High Availability, site resilience and disaster recovery feature. Adding multiple mailbox servers to the DAG and replicating all mailbox databases with other member servers will provide high availability at the database level. You will need at least two Mailbox Servers to configure DAG in Exchange 2010. Upon failure the database switch-over time is less than 30 seconds which will significantly improve the overall uptime.
Configure DAG in Exchange 2010
Configuring DAG (Database Availability Group) in Exchange 2010 is a straightforward process. Note following points before you start configuring DAG in Exchange 2010.
- A unique name for DAG is required which can be not more than 15 characters long.
- A dedicated additional IP address is recommended on the MAPI network subnet for the mailbox server.
- Installing Mailbox server role on at least two Exchange Servers.
- Exchange Server will automatically configure Hub Transport server as a witness server.
- Based on your scenario you might want to configure an alternate witness server.
Our environment involves the following setup
- MBG-CAS01: Running CAS and Hub Transport roles
- MBG-CAS02: Running CAS and Hub Transport roles
- MBG-MBX01: Running Mailbox Server role
- MBG-MBX02: Running Mailbox Server role
- DAG NAME: MBGDAG01
Below is the representation of our intended setup for configuring DAG:
Step 1: Configure Secondary Network Adapters (Replication Network adapter) on Mailbox Servers
Let us start with configuring the NIC on both Mailbox servers. DAG will require network connectivity for both client access and replication. Although a single network adapter simply works, it is recommended to have a dedicated network adapter for replication and MAPI traffic. To do this open Network Connections by typing ncpa.cpl in Run (Win Key + R). Right click on the Replication Network Adapter (the one you have it as secondary) and click on Properties.
In the replication network adapter properties on both mailbox servers, selec Internet Protocol Version 4 (TCP/IP4) and click Properties.
Now click on advanced button on the Internet Protocol Version 4 Properties page as shown below.
In the advanced TCP/IP settings navigate to DNS tab and uncheck the option “Register this connection’s address in DNS” as shown below and click OK.
Step 2: Configuring DAG from Exchange Management Console
From the Console Root Select Organization Configuration → Mailbox. In the right panel click on Database Availability Tab. From the action pane click on New Database Availability Group.
Type in the DAG name MBGDAG01 and click New.
Once the DAG is created successfully, the wizard will show the completion screen as shown below.
Now the DAG is ready we need to assign an IP Address, type the following command in the Exchange management shell. This IP should be fromt he
set-DatabaseAvailabilityGroup -Identity MBGDAG01 -DatabaseAvailabilityGroupIpAddresses 10.10.10.103
You may note that we have not specified any witness server in the New Database Availability Group wizard. However, Exchange will identify a Server with Hub Transport Role, select it as a witness server and creates the Witness Server folder automatically. As you can see in the below screenshot, DAG witness file share is created on MBG-CAS01 ( running both CAS and Hub Transport Roles).
We have created the DAG successfully, now we will have to add member servers to the DAG. From the Database Availability Group Tab right-click on the newly created DAG MBGDAG01 and click Manage Database Availability Group Membership.
Click on the +Add button to add member serves to the DAG. As per my scenario I will be selecting both MBG-MBX01 and MBG-MBX02 and adding them to the DAG, and then Click Manage
Configuring DAG through Exchange Management Shell:
Create a new DAG by using following command
New-DatabaseAvailabilityGroup -Name MBGDAG01 -DatabaseAvailabilityGroupIpAddresses 10.10.10.103
Add Member servers to the DAG by Issuing the following Command:
Add-DatabaseAvailabilityGroupServer -Identity MBGDAG01 -MailboxServer MBG-MBX02 Add-DatabaseAvailabilityGroupServer -Identity MBGDAG01 -MailboxServer MBG-MBX01
Step 03: Configure the DAG to Replicate Mailbox Databases only on the Replication Network
After adding both servers to the Database Availability Group, you will see the following in the Exchange Management Console:
The above screen shows that replication is enabled on both MAPI and Replication Network. But as per our scenario, we must enable replication only on a dedicated NIC configured for replication. To this right click on the MAPI network name and click properties as shown below.
In the MAPI network properties of the DAG, uncheck the option “Enable Replication” and then click OK as shown below.
Once you disable the replication on the MAPI network, now the database will only replicate on the Replication network (10.10.10.101/30). In this way you can configure DAG in exchange 2010.
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