Exchange 2010: Are Passive Database Copies Included in Backups of DAG Members?

In my article on backup error event id 2137 and what it means for Exchange 2010 a reader asked whether backups of Exchange 2010 DAG members include both the active and passive database copies.

Update: according to Microsoft, “All database copies can be backed up using an Exchange-aware, Volume Shadow Copy Service (VSS)-based backup application. However, the built-in support for Windows Server Backup is for active copies only. You can’t use Windows Server Backup to back up passive copies.” The rest of the article below has been left unedited, however be aware that the example demonstrated is of an unsupported scenario

The short answer is yes, however there are some important considerations to be aware of. From Microsoft TechNet:

Passive mailbox database copies are backed up using a separate VSS writer in the Microsoft Exchange Replication service. The Microsoft Exchange Replication service VSS Writer doesn’t support restores. Although you can back up a passive mailbox database copy using Microsoft System Center Data Protection Manager or a third-party Exchange-aware VSS-based application, you can’t perform a VSS restore directly to a passive mailbox database copy. However, you can perform a VSS restore to an alternate location, suspend replication to the passive copy, and then copy the database and log files from the alternate location to the location of the passive database copy in the file system.

To demonstrate this, here you can see the mailbox databases MB-HO-* that are currently active on server HO-EX2010-MB2. They have no LastFullBackup timestamp because they have never been backed up.

[PS] C:\>Get-MailboxDatabase -status | ft name,mounted*,lastfull* -auto

Name     MountedOnServer                     Mounted LastFullBackup
----     ---------------                     ------- --------------
MB-HO-01 HO-EX2010-MB2.exchangeserverpro.net    True
MB-HO-02 HO-EX2010-MB2.exchangeserverpro.net    True
MB-HO-03 HO-EX2010-MB2.exchangeserverpro.net    True
MB-BR-01 BR-EX2010-MB.exchangeserverpro.net     True

On server HO-EX2010-MB1 I ran a mailbox server backup using Windows Server Backup.

After the backup completed the following can be seen. First, the LastFullBackup time stamp has not been written.

[PS] C:\>Get-MailboxDatabase -status | ft name,mounted*,lastfull* -auto

Name     MountedOnServer                     Mounted LastFullBackup
----     ---------------                     ------- --------------
MB-HO-02 HO-EX2010-MB2.exchangeserverpro.net    True
MB-HO-01 HO-EX2010-MB2.exchangeserverpro.net    True
MB-HO-03 HO-EX2010-MB2.exchangeserverpro.net    True

Next, the disk that the backups were written to contain VHD files matching the size of the data stored on the backed up volumes. For example, the F: (Data) drive holds about 2Gb of data, and the VHD for that volume is about the same size.

Because we can mount the VHD as a disk on the server we have the opportunity to inspect the contents inside of it.

We can see that even though it was not the active databases at the time of the backup, the EDB file for database MB-HO-01 (and others) was still backed up by the server.

[PS] C:\>Get-ChildItem H: -Recurse | where {$_.name -like "*.edb"} | select name

Name
----
HO-PF-01.edb
MB-HO-01.edb
MB-HO-02.edb
MB-HO-03.edb
PF-HO-01.edb

Next I’ll run another backup of HO-EX2010-MB1, but this time the mailbox database MB-HO-01 has been made active on HO-EX2010-MB1.

This time the LastFullBackup time stamp is written to the database.

[PS] C:\>Get-MailboxDatabase -status | ft name,mounted*,lastfull* -auto

Name     MountedOnServer                     Mounted LastFullBackup
----     ---------------                     ------- --------------
MB-HO-01 HO-EX2010-MB1.exchangeserverpro.net    True 11/6/2011 1:40:19 PM
MB-HO-02 HO-EX2010-MB2.exchangeserverpro.net    True
MB-HO-03 HO-EX2010-MB2.exchangeserverpro.net    True
MB-BR-01 BR-EX2010-MB.exchangeserverpro.net     True

So what do we learn from this?

Reminder, the below should be read in conjunction with the notice at the start of the article, as backing up passive database copies using Windows Server Backup is not a supported scenario

• Yes, passive database copies stored on a volume are backed up by Windows Server Backup
• Yes, this allows backups of passive database copies to be restored, although not directly
• Yes, this would allow a backup of a passive database copy to be used for disaster recovery of a database
• No, the backup time stamp is not written when a passive database copy is backed up, so any monitoring of backups that involves checking that time stamp needs to take that into consideration