Restartable Active Directory is the ability to stop and restart Active Directory Domain Services without shutting down the domain controller. This allows you to apply updates to the domain controller or perform offline defragmentation of the AD DS database. It also allows services that do not depend on AD DS, such as DHCP, to continue functioning and responding to user requests. Restartable AD DS is available on all domain controllers that run Windows Server 2008, regardless of functional level.
Restartable AD DS makes it possible for a domain controller to be in any of the three states described in the table.
|AD DS Started||This is the state in which Active Directory is running and fully functional.|
|AD DS Stopped||This is the state in which Active Directory is stopped. A domain controller in this mode has the following characteristics:
|Directory Services Restore Mode||This state is almost identical to the Directory Services Restore Mode in Windows Server 2003. The one exception is that you can run the dcpromo /forceremoval command to remove AD DS from a domain controller running in DSRM. This is the state in which you must run the machine to restore Active Directory objects using the Ntdsutil utility.|
***You should know the following about restartable AD DS:
- You cannot start a Windows Server 2008 DC in the AD DS Stopped state, but you can restart it into DSRM.
- Services such as File Replication Service (FRS), Kerberos Key Distribution Center (KDC), and Intersite Messaging that depend on AD DS shut down before AD DS stops. If they are running when you stop AD DS, they restart when you restart AD DS.
- If the domain controller is a DNS server, it cannot respond to Active Directory-integrated zone queries while AD DS is stopped. To prevent DNS lookup failures, provide redundancy by configuring member computers, application servers, and domain controllers to point to multiple DNS servers.