When performing an Active Directory backup, what needs to be backed up, and should you back up all domain controllers?
Active Directory backups do not typically require organizations to back up every domain controller. Domain controllers replicate the Active Directory database to each domain controller in the domain. As such, the domain controllers within a domain can be thought of as being more or less equal.
The domain controllers that should be backed up depend on an organization's Active Directory structure. As a best practice, organizations should back up domain controllers that host Flexible Single Master Operations roles, as well as at least one domain controller that acts as a DNS server.
When backing up Active Directory in larger organizations, back up at least one domain controller in each domain. It might also prove beneficial to back up domain controllers that are acting as bridgehead servers for Active Directory sites, but doing so is not an absolute requirement.
This was first published in November 2012