Forest Recovery Restore Methods (4234548)

There are two methods for successfully restoring a Forest:

Recovery method 1: Restore as many domain controllers from backup as possible

To use this method you must have recent and trusted backups for as many domain controllers as possible in each domain in the forest. These backups must be created at a similar point in time to mitigate the risk of discrepancy after the forest is recovered. At a high level, Method 1 includes the following stages:

1. Recovery Manager for Active Directory Forest Edition restores as many domain controllers as possible in each domain from the recent and trusted backups you specify. The more domain controllers you restore from backups, the faster the forest recovery operation completes.
2. Recovery Manager for Active Directory Forest Edition uses Microsoft’s native tools (Dcpromo.exe or the Uninstall-ADDSDomainController and Install-ADDSDomainController cmdlets) to automatically reinstall Active Directory on the domain controllers for which no backups are available.
3. The domain controllers where Active Directory was reinstalled replicate AD data from the domain controllers restored from reliable backups.

Method 1 has the following advantages:

• Fast recovery of the entire forest. Since most domain controllers are simultaneously restored from backups, the forest recovery operation completes faster than in Method 2
• Stability of the forest recovery process. Owing to the large number of backups used, the entire forest is recovered even if the restore of some domain controllers fails
• This method allows you to retain the original forest infrastructure. Since many domain controllers are restored from backups, the recovered forest is close to its original prefailure condition

Method 1 has the following limitation:

• The risk of reintroducing corrupted or unwanted data is higher than in Method 2. Because of the large number of backups used in this method, there is no guarantee that corrupted or unwanted data from the backups will not be reintroduced into the recovered forest.

Recovery method 2: Restore one domain domain controller from backup in each domain

This recovery method is recommended by Microsoft in the Planning for Active Directory Forest Recovery paper. To use this method, you must have a recent and trusted backup for one domain controller in each domain in the forest. These backups must be created at a similar point in time to mitigate the risk of discrepancy after the forest is recovered. At a high level, recovering a forest using this method includes the following stages:

1. Recovery Manager for Active Directory Forest Edition restores one domain controller in each domain from the recent and trusted backup you specify.
2. Recovery Manager for Active Directory Forest Edition uses Microsoft’s native tools (Dcpromo.exe or the Uninstall-ADDSDomainController and Install-ADDSDomainController cmdlets) to automatically reinstall Active Directory on the domain controllers for which no backups are available
3. The domain controllers on which Active Directory was reinstalled replicate Active Directory data from the domain controllers restored from reliable backups

Method 2 has the following advantages:

• Recommended by Microsoft. This recovery method is recommended in the Microsoft’s bestpractice paper, Planning for Active Directory Forest Recovery
• Safer, healthier recovery as compared to Method 1. The limited number of backups used in Method 2 (one backup per each domain) allows you to check them all to make sure they do not include any corrupted or unwanted data

Method 2 has the following disadvantages:

• Forest recovery may require significant time to complete. Method 2 requires more time to complete than Method 1
• Recovery of entire domain depends on a successful restore of a single domain controller. A successful restore of one domain controller from backup is required before Active Directory can be reinstalled on all other domain controllers in the domain
• The original forest infrastructure is not retained. Because Active Directory is reinstalled on most domain controllers in the forest, the forest infrastructure cannot be restored to its exact pre-failure state

For a step by step procedure on how to perform a forest recovery, please see the Overview of steps to recover a forest section of the User Guide.