Friday, August 21, 2009

An Overview on Backing up and Restoring Active Directory

To ensure availability of mission critical resources and network objects, and business continuity, you would need to perform backups of Active Directory if it is running in your environment. This is because Active Directory normally hosts mission critical data, and resources. Backups are typically preformed for a number of reasons, including the following:

  • Protect your network environment from the accidental deletion of, or modification of data, and from hardware failures: Having a readily accessible back up of Active Directory would ensure that you can recover any important Active Directory objects which were deleted in error. Backups also prove invaluable when unauthorized users intentionally delete or modify data. The backup would enable you to restore data to its previous state of integrity. Because certain hardware failures such as corrupted hard disk drives can cause considerable loss of data, backing up your data would ensure that the business can continue to perform its mission critical functions when such an event does occur.

Store mission critical data: It is recommended to regularly back up mission critical data so that any previous version of information can be accessed, if necessary, at some time in the future
because Active Directory is dependent on the Registry, you need to back up files within the system directory. These files are called system files. System state data basically contains the main configuration information in Windows 2000, and Windows Server 2003. What actual information is included in system state data is determined by operating system (OS) configuration.

System state typically includes the following important data, files and components:
  • The Windows Registry
  • The contents of the SYSVOL directory
  • Files which are protected by the Windows File Protection system
  • Boot and system files: Ntdetect.com, Ntldr and Bootsect.dat.
  • The COM+ Class Registration database
  • The Active Directory database (Ntds.dit), including all log files and checkpoint files
  • Cluster service files
  • Certificate service files
  • The Internet Information Server (IIS) metabase
You can use one of the methods listed below to back up Active Directory.
  • You can back up the system state data only
  • You can back up Active Directory as part of a full system backup
  • You can back up Active Directory as part of a partial system backup
The best option to use when specifying what data or components should be backed up in the Active Directory backup; is to specify a back up of system state data. This ensures that all core system files are backed up. When a full system backup is performed, system state data is automatically included in the back up process. When performing a partial backup, you can specify that system state data should be included. Manually specifying individual files and components for an Active Directory backup can be an extremely complicated process. Apart from having to be able to identify and specify all important system files and

components, you also need to be able to specify which other important Active Directory data and components need to be backed up, such as the replication topology, and Group Policy information. You can back up Active Directory by using the Windows Server 2003 Backup utility, or you from the command line, using the Ntdsutil command-line utility. The Windows Server 2003 Backup utility includes the feature of using volume shadow copying to back up open files. With the previous versions of Windows, a third party backup tool had to be used to back up open files. The Volume Shadow Copy service creates a read-only copy of any open files. This in turn ensures that these files can continue to be accessed. In Windows 2000 Active Directory, you could only perform one of the following restore methods:
  • Authoritative Restore
  • Non- Authoritative
When it comes to restoring Windows Server 2003 Active Directory, you can use one of the following restore methods:
  • Normal Restore: In Windows 2000, this was your Non-Authoritative restore method. A Normal restore functions pretty much the same as a Non-Authoritative restore. With a Normal restore, the Backup utility is run on the computer while in Directory Services Restore Mode. After the domain controller is rebooted, normal replication occurs with replication partners.
A normal restore is typically performed when the following conditions exist:
o A domain has multiple domain controllers, and only one domain controller is operational. You can use a Normal restore to restore all other domain controllers in the domain.
o A domain has a single domain controller, and that domain controller has to be restored. You can also choose to alternatively perform a Primary restore of Active Directory.

  • Authoritative Restore: An Authoritative restore of Active Directory has to be performed in cases where a Normal restore would not be able to return Active Directory to the correct state. For instance, if an organizational unit was deleted in error, a Normal restore would only result in the particular OU being deleted once again, after replication. This is basically due to the replication partners having a higher version number for the particular OU. An Authoritative restore has a similar process to that of a Normal restore, the difference being that after system data is restored, you define certain Active Directory objects as being authoritative. When Active Directory objects are defined as authoritative, the particular objects have the higher version numbers. This results in these objects being replicated to the other domain controller’s copies of the Active Directory database.
  • Primary Restore: The Primary restore method is used when each domain controller within a domain hosting multiple domain controllers, needs to be restored. What this means is that the entire domain has to be reconstructed from the Active Directory backup. This method can also be used to restore Active Directory for a domain that only has one domain controller. The Primary restore method is selected in Windows Server 2003 Backup utility by merely enabling the Primary restore method checkbox. This removes previous complexities associated with performing this type of restore in Windows 2000. The Primary restore process is also very similar to that performed for a Normal restore of Active Directory.

1 comment:

Anonymous said...

Good jod thatte.....