Saturday, 31 July 2010 19:15

Configure and Manage Database Availability Groups

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DAG (Database Availability Group) is the answer for Exchange 2010 database high availability. The Database Availability Group is a set of up to 16 exchange 2010 mailbox servers which gives automatic database-level recovery from a Database, Server or Network failures. If you are new to DAG concept see Database Availability Group.

In this blog we will see how to configure the Database Availability Group. We will be covering the following aspects,
  • Configure Databases
  • Create New DAG(Database Availability Group)
  • Add Mailbox Servers into DAG (Add members)
  • Managing DAG.
My Lab Server Details:
Domain Controller: EXCHDIC-DC01
Exchange Servers: EXCHDIC-EX01
                              EXCHDIC-EX02
Before we start creating the Database Availability Group, let us create 1 database each on both servers.
  1. Create a folder to keep the EDB and log files of the new database(E:\DB01) on the Server EXCHDIC-EX01
  2. Open Exchange Management Shell
  3. Run the cmdlet:- New-MailboxDatabase -Name DB01 -EDBFilepath "E:\DB01\DB01.edb"-LogFolderPath       "E:\DB01" -Server EXCHDIC-EX01 
  4. Repeat the above steps in EXCHDIC-EX02 (Create folder called E:\DB01 in the server EXCHDIC-EX02 and run the shell command)
  5. New-MailboxDatabase -Name DB02 -EDBFilepath "E:\DB02\DB02.edb" -LogFolderPath "E:\DB02" -Server EXCHDIC-EX02  

New Mailbox Database - DAG

Ensure that both the databases are mounted.

High Availability – Mailbox

Few things to notice before we configure the DAG.

  • Exchange 2010 doesn't use the concept of a clustered mailbox server (referred to as an Exchange Virtual Server in Exchange Server 2003 and earlier). As a result, Exchange is no longer a clustered application, and Exchange server identities no longer move between clustered servers.
  • Exchange 2010 doesn't use the concept of storage groups
  • Exchange 2010 doesn't use the concepts of public and private networks. These concepts are replaced with the concepts of MAPI networks and replication networks. Each DAG should contain one MAPI network and one or more replication networks.

Create and Configure the Database Availability Group

Open ADUC(Active Directory Users and Computers) and modify the security membership as below.

  1. Go to Microsoft Exchange Security Groups Container.
  2. Add “Exchange trusted Subsystem” Group to Builtin\Administrators group.
  3. Add Computer object EXCHDIC-DC01 to “Exchange servers” group.
If you are planning to use one of your Exchange 2010 server as Witness Server then you don't require perform the 3rd step. Here we have planned to use out Domain Controller as the Witness server and the Witness Server should be a part of “Exchange servers” group.
  • Run the given command to create a new Database Availability Group.
  • New-DatabaseAvailabilityGroup  -name ExchDICDAG1 -WitnessServer EXCHDIC-DC01 -WitnessDirectory C:\DAG1 -DatabaseAvailabilityGroupIPAddresses 10.10.10.15

New Database Availability Group

  • Add the Exchange Servers into the newly created DAG.

On the Server EXCHDIC-EX01
Add-DatabaseAvailabilityGroupServer -Id ExchDICDAG1 -mailboxserver EXCHDIC-EX01
On the Server EXCHDIC-EX02
Add-DatabaseAvailabilityGroupServer -Id ExchDICDAG1 -mailboxserver EXCHDIC-EX02

Adding into DAG Membership

The above steps will configure DAG and the Failover Cluster if it is not installed. That means when we add a server as a member into the DAG the cluster service is automatically installed.  

    • Add the database copy
      • Add-MailboxDatabaseCopy -Identity DB01 -MailboxServer EXCHDIC-EX02
      Add Mailbox Database Copy - DAG
        • Verify the Status of newly created database copy

          Open EMC and navigate to Organization Configuration -> Mailbox and select the tab Database Management. Select the database DB01.

          DAG Mailbox Database Copy Status
          We also can use the cmdlet mentioned below to see the status of database copy.
          Get-MailboxDatabaseCopyStatus -Identity DB01      

          End User Experience Database Availability Group
          When a user accessig his/her mailbox that was hosted on a DAG mailbox database during a swithover or a failover, he/she will see the below message.

          End User Experience - During Failover      
          Click on Inbox again after a few more seconds, he/she will be able to access his mailbox without re-logging in to the mailbox.

          End User Experience - After Failover

          The failover/swithover is much faster comparing to the previous version of exchange.

          You can also use the EMC to create and manage Database Availability Group. For that open  EMC(Exchange Management Console) and navigate to Organization Configuration -> Mailbox and select the tab Database Availability Groups.

          Enjoy !

          -Praveen    

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