If a domain controller is rolled back in time outside of the domain controller’s awareness and a USN is reused for an entirely different transaction, replication will not converge because other domain controllers will believe they have already received the updates associated with the re-used USN under the context of that InvocationID.įor example, the following illustration shows the sequence of events that occurs in Windows Server 2008 R2 and earlier operating systems when USN rollback is detected on VDC2, the destination domain controller that is running on a virtual machine. The InvocationID of a domain controller and its USN together serve as a unique identifier associated with every write-transaction performed on each domain controller and must be unique within the forest.ĪD DS replication uses InvocationID and USNs on each domain controller to determine what changes need to be replicated to other domain controllers. Each domain controller’s database instance is also given an identity, known as an InvocationID. AD DS replication, for example, uses a monotonically increasing value (known as a USN or Update Sequence Number) assigned to transactions on each domain controller. Virtual environments present unique challenges to distributed workloads that depend upon a logical clock-based replication scheme. Steps for deploying a clone virtualized domain controller Safe virtualization of domain controllers These new virtualization features provide greater support for public and private clouds, hybrid environments where portions of AD DS exist on-premises and in the cloud, and AD DS infrastructures that reside completely on-premises. Beginning with Windows Server® 2012, AD DS provides greater support for virtualizing domain controllers by introducing virtualization-safe capabilities and enabling rapid deployment of virtual domain controllers through cloning.

Virtualization of Active Directory Domain Services (AD DS) environments has been ongoing for a number of years. Introduction to Active Directory Domain Services (AD DS) Virtualization (Level 100)

Pro 100 С