Active Directory improvements in Windows Server 2008: Rebootable AD DS

Administrators can stop or restart AD DS through the MMC snap-in or the command line in Windows Server 2008.

What can a restartable AD DS do?

A restartable AD DS can reduce the time it takes to perform a specific operation. AD DS can be stopped, so updates can be applied to domain controllers. Of course, the administrator can stop AD DS to perform tasks such as offline defragmenting the AD database without restarting the domain controller. Other services running on the server do not rely on AD DS to work, such as the DHCP service, so they can continue to satisfy the client's request when AD DS stops servicing.

Are there any other special considerations?

AD DS that can be restarted on all domain controllers running Windows Server 2008 is valid by default. There are no functional levels or other required requirements for using this feature.

What new features does this feature offer?

In Windows Server 2000 or Windows Server 2003 Active Directory, offline database defragmentation requires a domain controller to be restarted to the directory service recovery mode. Applying security updates also often requires a domain controller to be restarted.

However, in Windows Server 2008, administrators can stop or restart AD DS. This makes it possible to perform AD DS offline operations more quickly.

The restartable AD DS adds some minor changes to the existing MMC snap-in. A domain controller running Windows Server 2008 Active Directory can perform the task of restarting AD DS in both the Service Management Unit and the Computer Management Unit. With the snap-in, administrators can simply stop or restart AD DS as if they were managing other local services running on the server.

What happened to the existing features?

While stopping AD DS and logging in to Directory Services Restore mode, restartable AD DS provides a unique state for domain controllers running Windows Server 2008. In this state it is called AD DS stop.

The following are three possible states for running Windows Server 2008 domain controllers: AD DS startup. This state means that AD DS has started. For users or other services running on the server, the Windows Server 2008 domain controller running in this state is like a domain controller running on Windows 2000 Server and Windows Server 2003.

AD DS stops. This state means that this AD DS has stopped. Although this mode is unique, servers running in this state have both domain controllers in directory restore mode and certain features of member servers that have joined the domain.

As Directory Services Restore Mode (DSRM), the Active Directory database (Ntds.dit) located on the local domain controller is offline. If another domain controller is available, the local domain controller can contact it to log in. If there are no other available domain controllers. If you are unable to contact other domain controllers, you can use the Directory Services Restore Mode password to log in to the local domain controller in Directory Services Restore mode.

As a member server, the server is joined to the domain. This means that Group Policy or other settings are still being applied to changing the computer. However, the domain controller should not remain in this state for a long time because the domain controller cannot service the login request or perform replication operations with other domain controllers.

Directory service restore mode. This mode (state) is the same as the directory service restore mode under Windows Server 2003 and has not changed.

The following flow chart shows how a domain controller running Windows Server 2008 can change between these three states.
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