Tag Archives: DAG

How to Use Windows Server Backup to back up Exchange 2010 Database Availability Groups (DAG)

Unless you’re comfortable with entrusting your data to DAG & circular logging, backing up Exchange 2010 on a routine basis is critical in order to protect your data and truncate the database logs.

While Microsoft has several articles on using Windows Backup for Exchange 2010, none of them really spell out a start to finish solution for a DAG environment.

In order to configure Windows Backup for an Exchange 2010 environment employing DAG’s, the following need to be accomplished.

  1. If not installed already, install the Windows Server Backup Feature, but NOT the command line tools (those are still 32-bit and incompatible)
  2. Uninstall the Windows Server Backup Features “Command-line Tools” if installed.
  3. Create a registry entry to disable the Microsoft Exchange Replication service VSS writer (see below for step-by-step).
  4. Restart the Microsoft Exchange Replication service.
  5. Set to Automatic and then start the Microsoft Exchange Server Extension for Windows Server Backup service.
  6. Configure your backup using Windows Server Backup (see below for step-by-step).

Registry Change

This was taken from http://technet.microsoft.com/en-us/library/dd876851.aspx which has additional information on using Windows Backup with Exchange 2010… I highly encourage everyone responsible for their Exchange environment to read it thoroughly:

If a server hosting the data being backed up is a member of a database availability group (DAG) and hosts both active and passive database copies, you must disable the Microsoft Exchange Replication service VSS writer. If the Microsoft Exchange Replication service VSS writer is enabled, the backup operation will fail.

To disable the Microsoft Exchange Replication service VSS writer, perform the following steps:

  1. Log on to the server by using an account that has local administrator access, and then start Registry Editor (regedit).
  2. Navigate to HKEY_LOCAL_MACHINE\Software\Microsoft\ExchangeServer\v14\Replay\Parameters.
  3. Add a new DWORD value named EnableVSSWriter, and set its value to 0.
  4. Exit Registry Editor and then restart the Microsoft Exchange Replication service.

Configure Windows Backup

You only need to specify the drives that have an Exchange database on them that you wish to backup.  In my environment, I have one database per drive, and I only back up the drives that typically run the Active copy of the database.   i.e. every Exchange mailbox server in my environment has a Windows Backup job configured to back up only the drives that have an active database.  There is no reason to back up the passive database copies on every server.

By configuring it this way, that Exchange Agent for Windows Backup automatically knows that you’ve backed up the database and will truncate the logs shortly after the backup completes on all servers in the DAG.

The following was taken from http://technet.microsoft.com/en-us/library/dd876854.aspx which has additional information on using Windows Backup with Exchange 2010… Again, I highly encourage everyone responsible for their Exchange environment to read it thoroughly:

You need to be assigned permissions before you can perform this procedure. To see what permissions you need, see the “Mailbox recovery” entry in the Mailbox Permissions topic.

  1. Start Windows Server Backup.
  2. In the Actions pane, click “Configure Performance Settings…”
  3. Change the Performance Settings to Custom, and then configure at least your DAG volumes to Incremental, though I would recommending changing all volumes to Incremental (this will cause a fresh, full backup to occur every 14 days)
  4. In the Actions pane, click Backup Once. The Backup Once wizard appears.
  5. On the Backup options page, select Different options, and then click Next.
  6. On the Select backup configuration page, select the type of backup that you want, and then click Next.
    1. Select Full server (recommended) to back up all volumes on the server.
    2. Or, select Custom to specify which volumes should be included in the backup. If you select this option, the Select backup items page appears. Select the volumes to be backed up, and then click Next.
  7. On the Specify destination type page, select the location where you want to store the backup, and then click Next. If Remote shared folder is selected, the Specify remote folder page appears. Specify a UNC path for the backup files, and then do one of the following to configure access control settings:
    1. Select Do not inherit if you want the backup to be accessible only by a set of specified user credentials, and then click Next. Type a user name and password for a user account that has write permissions on the computer that is hosting the remote folder, and then click OK.
    2. Or, select Inherit if you want the backup to be accessible by everyone who has access to the remote folder, and then click Next.
  8. On the Specify advanced options page, select VSS full backup, and then click Next.
  9. On the Confirmation page, review the backup settings, and then click Backup.
  10. On the Backup progress page, you can view the status and progress of the backup operation.
  11. Click Close when the backup operation has completed.

Exchange 2010 Database Accessability Group Witness Server Requirements

In the Exchange Server 2010 Database Accessibility Group (DAG) documentation (http://technet.microsoft.com/en-us/library/dd298065.aspx), it states the following:

“The witness server and its directory are used only for quorum purposes where there’s an even number of members in the DAG.”

This is semi-confusing during the planning stages of an Exchange 2010 infrastructure, as you must have a witness server regardless of how many mailbox servers are members of a DAG.  It’s just that the witness only comes in to play when their are an even number of active members in a DAG.

Even a little more confusing is that a witness server is typically just an Exchange Hub Transport server that does not have the mailbox role installed (i.e. a Witness can never host a copy of the database it’s witnessing).  So, if your environment consists of dedicated mailbox servers separated from the Client Access and Hub Transport roles, you really don’t have to install any additional servers.

In our environment, we’re taking Microsoft’s recommendation of using only mutli-role servers, so we had to set up a dedicated Hub Transport server to act as the Witness for our DAG.

While you can set up a Windows Server as a witness without Exchange installed on it (see the above article), it’s really not a good idea as that prevents your Exchange administrators from properly managing the entire environment from within Exchange (and we get cranky when we can’t control everything).

Additionally, while your mailbox-role servers must be running the Enterprise Edition of Windows Server to be a part of the DAG, the Hub Transport (Witness) server does not need to be running Enterprise Edition, even though it is a proper part of the DAG.