Backing up data is never a bad idea since it can provide handy insurance against accidental data loss. The DFS Replication service is designed to interoperate with the backup/restore interfaces exposed by the Windows Volume Shadow Copy Service (VSS). This facilitates consistent backup and restore operations on replicated data.
This series of blog posts explore how backups can be taken of replicated data and the manner in which data can be restored. This first article explains a few backup/restore specific terms that will be used frequently in the following articles in the series.
System State Backup (Critical Volumes Backup)
System state includes more data on Windows Server 2008 than in the Windows Server 2003 operating system. In Windows Server 2008, the system components which contribute to system state may depend on the configuration of the computer. System state data includes at least the following and may include additional data that is configuration dependent:
System state cannot be backed up separately – critical volumes (volumes storing system components including NTDS.dit, SYSVOL and %windir%) can be backed up. On domain controllers which are using the DFS Replication service for SYSVOL replication (i.e. Windows Server 2008 domain functional level), the DFS Replication service co-operates with Windows Server Backup in order to backup the SYSVOL folder.
The non-authoritative restore process is performed in the Windows Recovery Environment, which operates from the Microsoft Windows Pre-installation Environment (Windows PE). This environment can be accessed from the Windows Server 2008 setup media. System State Backups can be taken using Windows Backup by selecting all critical volumes on the server. This method can be used to backup a domain controller that uses DFS Replication for replicating the contents of the SYSVOL share.
It is recommended to take scheduled backups onto a volume that is hosted on a different hard disk. However, manual backups can be made to a volume on the same hard disk, as long as that destination volume is not included in the backup. Scheduled backup reformats the destination volume and therefore a dedicated backup volume is recommended. Manual backups, on the other hand, do not reformat the destination volume. Windows Server Backup also supports the usage of DVDs as backup media.
Full Server Backup
A full server backup is a backup of every volume on the server. For instance, this type of backup can be used to recover a server onto new hardware.
By authoritatively restoring the contents of a replicated folder, you are specifying that the copy of the data that is restored from the backup is authoritative for the replication group. After the restore operation replaces data from the backup in the replicated folder, the DFS Replication service marks the restored data as authoritative and it is replicated to the other member servers in that replication group.
An authoritative restore of replicated data is performed when recovering from a situation where human error is involved and the error has replicated to other member servers in the replication group. For example, you might perform an authoritative restore if an administrator has accidentally deleted some files/folders that reside in the replicated folder.
When you non-authoritatively restore the contents of a replicated folder, the local copy of data on the restored replication member server is compared with that of its replication partners. Any necessary changes are then replicated in, thus bringing the local data up-to-date with the other replication partners in the replication group.
Perform a non-authoritative restore if at least one other functioning replication member server exists in the replication group. This is the default method for restoring data in the replicated folder and occurs if the DFS Replication service is not explicitly instructed to perform an authoritative restore.
Installing Windows Server Backup
One of the tools that can be used to perform a backup/restore operation of DFSR replicated data on Windows Server 2008 is Windows Server Backup. Windows Server Backup is an optional component which can be installed from the Server Manager.
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