Thursday 29 July 2021

Backing up a Windows Domain Controller

This will depend on number of domain controllers you have but the over all idea is that if you have a DC running on your network it is best practise to use backup software that is Application aware as restoring the DC in a crash consistent state may lead to data lost within the Active Directory.

Single Domain Controller network
Application Aware backup can be optional but really why chance it.  If the backup that was taken was not application aware it may suffer data lost but should be ok ish.

Multi Domain Controller network
100% Application aware,  if you restore a single DC in to a network with multiple DC you will end up triggering a USN Rollback and this is a silent error.

Also if you are restoring the DC the backups age can be no longer then the AD tombstone lifetime or again you will have issues.

If the DC is 2012 or higher it has added support for Hyper-Visor Generation ID (GenID). This allows the virtual guest to detect the disk volumes that have a new ID, and respond to the new GenID. In Active Directory, Directory Services reacts as if the domain controller was restored from a backup. It then generates a new Invocation ID. By using the new Invocation ID, the database instance can to safely re-enter replication in the forest.

Virtualizing Domain Controllers using Hyper-V | Microsoft Docs

Virtual Active Directory Domain Services Domain Controllers Hyper-V | Microsoft Docs

Determine the tombstone lifetime for the forest | Microsoft Docs

How to detect and recover from a USN rollback in a Windows Server-based domain controller - Windows Server | Microsoft Docs

How to back up and restore domain controllers on Hyper-V (altaro.com)

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