About Microsoft DFSR backups

Microsoft Distributed File System Replication (DFSR) service is a multi-master replication engine that is used to keep folders synchronized on multiple servers. To do this, each of these independent DFSR servers maintains a database which is essential in providing this service but is independent of the DFSR data that is being replicated. AlthoughNetBackup protects this database, as well as the DFSR data, there are some things to consider when restoring both.

A DFSR server maintains information in its database that is used by other DFSR servers to identify and validate replication changes that may be needed. One bit of information is a globally unique version number (GVSN), which increases monotonically with every replicated file or folder alteration. It can be thought of as a version or generation number for each DFSR database on each replicated volume.

A problem occurs if a DFSR server is restored to an earlier database version. The other servers, which monitor and remember each other's numbers, will be confused when presented with the older number. At this point replication is impossible and will stop until this is corrected. Consider carefully if your restore actually needs to include the DFSR database, in addition to the DFSR data. This is likely to happen if you have a virtualized DFSR server and you restore it to a snapshot that had been taken earlier. Please refer to the Microsoft documentation on managing and using DFSR for additional details.

In an environment that has DFSR, two changes occur in NetBackup, as follows:

To preserve data integrity, the folder or folders that host the Shared Replica DFSR data are excluded automatically by NetBackup from normal file system backups.
The top-level DFSR shared folders become part of the Shadow Copy Components. Therefore, the data is snapped consistently by Windows Volume Shadow Copy Service (VSS) before each backup.

Microsoft supports only the VSS writer for DFSR managed data backups. The VSS writer stops and restarts the DFS Replication service automatically. Veritas recommends that you schedule the backups to coincide with a period of low activity. (If you stop the replication service manually, Microsoft change journal problems may occur. Specifically, Update Sequence Number (USN) Journal wrap may occur.)

Veritas recommends that you back up DFSR data based on the amount of data under DFSR control as described in Table: Microsoft DFSR backup recommendations.

Table: Microsoft DFSR backup recommendations

Amount of data	Veritas recommendation
Less than 50 GBs	Configure one policy as follows: Choose the DFSR server host as the client. See Adding, changing, or deleting clients in a policy. Choose ALL_LOCAL_DRIVES as the Directive in the Backup Selections for the policy. The ALL_LOCAL_DRIVES directive includes the Shadow Copy Components:\ automatically. See Adding backup selections to a policy. One policy can back up the data within a reasonable time window.
More than 50 GBs	Configure one backup policy for each DFSR server, and in that policy specify only the replication folders. A policy for each host's replication data ensures that the DFSR data is backed up within a reasonable time window. For each DFSR server host, do the following: Create a global exclude list for All Policies and All Schedules. Exclude the following DFSR top-level folder: `Shadow Copy Components:\User Data\Distributed File System Replication\DfsrReplicatedFolder` The global exclude list ensures that the DFSR components are not backed up accidentally by other backup policies for the client. See Exclude Lists properties. Create a backup policy for the DFSR data, as follows: For the client, specify the DFSR server host. For the servers that are hosted in a cluster, specify the DFSR cluster name rather than the local host name. See Adding, changing, or deleting clients in a policy. For the Backup Selections for the policy, specify the absolute path to each of the top-level DFSR folders on that host. The following is an example path: `Shadow Copy Components:\User Data\Distributed File System Replication\DfsrReplicatedFolders\folder_name` Tip: Use the Backup, Archive, and Restore interface to browse the Shadow Copy Components for the `DfsrReplicatedFolders` folder. The interface shows the path to each DFSR folder that you need to enter as a backup selection. See Adding backup selections to a policy. For the backup policy, create an exception to the exclude list and specify the top-level DFSR directory, as follows: `Shadow Copy Components:\User Data\Distributed File System Replication\DfsrReplicatedFolders` For the exception Policy, specify the backup policy for the DFSR data. Also specify All Schedules for the Schedule. If DFSR is hosted in a cluster, create the exception for each host in the cluster. The exception ensures that the Shadow Copy Components DFSR paths are included for backup after NetBackup processes the global exclude list. See Adding an exception to the exclude list.

Amount of data

Veritas recommendation

Less than 50 GBs

Configure one policy as follows:

Choose the DFSR server host as the client.
See Adding, changing, or deleting clients in a policy.
Choose ALL_LOCAL_DRIVES as the Directive in the Backup Selections for the policy.
The ALL_LOCAL_DRIVES directive includes the Shadow Copy Components:\ automatically.
See Adding backup selections to a policy.

One policy can back up the data within a reasonable time window.

More than 50 GBs

Configure one backup policy for each DFSR server, and in that policy specify only the replication folders. A policy for each host's replication data ensures that the DFSR data is backed up within a reasonable time window.

For each DFSR server host, do the following:

Create a global exclude list for All Policies and All Schedules. Exclude the following DFSR top-level folder:
Shadow Copy Components:\User Data\Distributed File System Replication\DfsrReplicatedFolder
The global exclude list ensures that the DFSR components are not backed up accidentally by other backup policies for the client.
See Exclude Lists properties.
Create a backup policy for the DFSR data, as follows:
- For the client, specify the DFSR server host. For the servers that are hosted in a cluster, specify the DFSR cluster name rather than the local host name.
  See Adding, changing, or deleting clients in a policy.
- For the Backup Selections for the policy, specify the absolute path to each of the top-level DFSR folders on that host. The following is an example path:
  Shadow Copy Components:\User Data\Distributed File System Replication\DfsrReplicatedFolders\folder_name
  Tip: Use the Backup, Archive, and Restore interface to browse the Shadow Copy Components for the DfsrReplicatedFolders folder. The interface shows the path to each DFSR folder that you need to enter as a backup selection.
  See Adding backup selections to a policy.
For the backup policy, create an exception to the exclude list and specify the top-level DFSR directory, as follows:
Shadow Copy Components:\User Data\Distributed File System Replication\DfsrReplicatedFolders
For the exception Policy, specify the backup policy for the DFSR data. Also specify All Schedules for the Schedule.
If DFSR is hosted in a cluster, create the exception for each host in the cluster.
The exception ensures that the Shadow Copy Components DFSR paths are included for backup after NetBackup processes the global exclude list.
See Adding an exception to the exclude list.

The DFSR servers must be configured for Windows Open File Backup. The snapshot provider must be Volume Shadow Copy Service. Configure these properties in the NetBackup Administration Console master server host properties Client Attributes tab.

See Windows Open File Backup tab of the Client Attributes properties.

During a backup, Windows writes the following event ID messages to the application event log of a DFSR host:

Event ID=1102 
Severity=Informational 
The DFS Replication service has temporarily stopped replication 
because another application is performing a backup or restore 
operation. Replication will resume after the backup or restore 
operation has finished.

Event ID=1104 
Severity=Informational 
The DFS Replication service successfully restarted replication 
after a backup or restore operation.

To restore DFSR data, use the NetBackup Backup, Archive and Restore client interface to browse the Shadow Copy Components for the files or folders to restore, as follows:

Shadow Copy Components:\User Data\Distributed File System Replication\DfsrReplicatedFolders\folder_name

The following Veritas article provides a more detailed procedure about configuring DFSR backups:

http://www.veritas.com/docs/HOWTO65638

About Microsoft DFSR backups

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