SYSVOL Migration States

[アーティクル]
07/02/2012

Updated: April 15, 2009

Applies To: Windows Server 2008, Windows Server 2008 R2

The migration process proceeds through a number of states, during which SYSVOL replication transitions from using File Replication Service (FRS) to using Distributed File System Replication (DFS Replication). This transition takes place in discrete steps, as described in the following sections.

Global and local migration states
Migration states
How DFS Replication migrates between states

Global and local migration states

Because the migration process involves setting migration directives on the domain controller that is the Primary Domain Controller (PDC) emulator and waiting for the other domain controllers to carry out those directives, migration states can either be global to the domain or local to an individual domain controller:

Global The global migration state is the migration state that you set with the dfsrmig command to initiate one of the phases of the migration process. After you set the global state, which is stored in Active Directory Domain Services (AD DS), it replicates to all domain controllers.

For more information about the dfsrmig command, see Dfsrmig.
Local Each domain controller has a local migration state. DFS Replication on each domain controller polls AD DS to determine the global migration state to which the domain controller should migrate. If the global migration state differs from the local state on the domain controller, DFS Replication attempts to transition the local state to match the global state. The local migration state can be one of the stable states or the transition states that are described later in this section.

Migration states

The SYSVOL migration process is a state-based process that progresses through four primary (stable) states, as well as six temporary (transition) states that individual domain controllers progress through to reach the stable states.

Stable states

There are four stable states, which are in effect the four phases of migration. These states are similar to the process that occurs when employees of a company plan to retire or leave the company, and they train other employees to assume their responsibilities. The similarities in these processes are described in the following table.

State	Transition Process for Job Responsibilities	Migration Process for SYSVOL Replication
Start (State 0)	Before deciding to retire or leave, the employee handles all of the responsibilities of the job.	Before SYSVOL migration begins, FRS replicates the SYSVOL shared folder.
Prepared (State 1)	The first employee continues working while the new employee shadows the first employee, learning how to perform the work. The new employee may become responsible for some minor tasks, but the first employee remains accountable for the primary responsibilities of the job.	FRS continues to replicate the SYSVOL shared folder that the domain uses, while DFS Replication replicates a copy of the SYSVOL folder. This copy of the SYSVOL folder is not used to service requests from other domain controllers.
Redirected (State 2)	The new employee takes over most of the responsibilities of the job, but the first employee remains to assist the new employee if needed.	The DFS Replication copy of the SYSVOL folder becomes responsible for servicing SYSVOL requests from other domain controllers. FRS continues to replicate the original SYSVOL folder, but DFS Replication now replicates the production SYSVOL folder that domain controllers in the Redirected state use.
Eliminated (State 3)	The first employee retires or leaves, and the new employee handles all of the responsibilities of the job.	DFS Replication continues to handle all the SYSVOL replication. Windows deletes the original SYSVOL folder, and FRS no longer replicates SYSVOL data.

You use the dfsrmig command during migration to step through the four stable states. The significant changes in SYSVOL replication that occur during these phases and that are most visible to users include the following events:

The migration process creates a copy of the SYSVOL folder.

FRS continues to replicate the original SYSVOL folder, which is located by default at [drive:\]Windows_folder\SYSVOL. DFS Replication replicates the copy of the SYSVOL folder, which is located by default at [drive:\]Windows_folder\SYSVOL_DFSR.
The mapping of the SYSVOL shared folder changes.

This mapping controls whether the SYSVOL information that the domain actively uses is replicated by FRS or DFS Replication. Originally, the SYSVOL shared folder maps to [drive:\]Windows_folder\SYSVOL, so the SYSVOL information that the domain actively uses is replicated by FRS. Later in the migration process, the SYSVOL shared folder maps to [drive:\]Windows_folder\SYSVOL_DFSR, and the SYSVOL information that the domain actively uses is replicated by DFS Replication.
The migration process deletes the original copy of the SYSVOL folder.

The following table shows the stable states during the migration process.

State number	State	[drive:\]Windows_folder\SYSVOL Folder	[drive:\]Windows_folder\SYSVOL_DFRS Folder	SYSVOL Shared Folder Mapping
0	Start	Present, contains content, and replicated by FRS.	Not present, unless migration was rolled back. Not replicated if present.	[drive:\]Windows_folder\SYSVOL
1	Prepared	Present, contains content, and replicated by FRS.	Present, contains content, and replicated by DFS Replication.	[drive:\]Windows_folder\SYSVOL
2	Redirected	Present, contains content, and replicated by FRS.	Present, contains content, and replicated by DFS Replication.	[drive:\]Windows_folder\SYSVOL_DFSR
3	Eliminated	Absent, unless the folder was open during migration to the eliminated state. If present, contains no files and is not replicated.	Present, contains content, and replicated by DFS Replication.	[drive:\]Windows_folder\SYSVOL_DFSR

Local Transition states

During migration, each domain controller cycles through intermediate states before reaching one of the stable states described in “Stable states” earlier in this document. The following table lists these local transition states.

State number	Transition state name
4	Preparing
5	Waiting for initial synchronization
6	Redirecting
7	Eliminating
8	Undo redirecting
9	Undo preparing

Note

The Preparing state is only applicable to read-only domain controllers (RODCs).

How DFS Replication migrates between states

The DFS Replication service on each domain controller polls AD DS for the current global migration state. If the global state differs from the local state on the domain controller, DFS Replication takes steps to change its local state to match the global state.

You use the dfsrmig command to migrate domain controllers from the Start state to each subsequent stable state until the domain controllers reach the Eliminated state. Before domain controllers migrate to the Eliminated state, you can reverse the migration if needed either completely back to the Start state or partially back to a previous stable transition state. This process is called rollback.

For example, if the global migration state in the domain is Redirected, you can choose to roll back to either the Prepared state or the Start state. After you move to the Eliminated state, however, you cannot roll back the migration. Therefore, you should move to the Eliminated state only if you are absolutely sure that the DFS replication of SYSVOL works satisfactorily and that you are fully committed to switch to DFS Replication.

State transitions during migration and rollback

Figure 1 shows the states through which the migration process moves. The large circles represent the four stable migration states. The small circles represent the transition states that a domain controller passes through to reach the stable states.

Figure 1 Moving forward through migration states

Figure 2 shows the states through which domain controllers move during the rollback process. The large circles represent stable migration states. The small circles represent the transition states that a domain controller passes through during the roll back to one of the stable states.

Figure 2 Moving backwards in migration states