For security and performance reasons, we recommend that you do not install a standalone SQL Server on a domain controller.

Regarding  failover cluster, SQL instances are not supported where cluster nodes are domain controllers.

Other point, a read-only domain controller (RODC) is a new type of domain controller in the Windows 2008. SQL Server is not supported on a read-only domain controller.

Current resolution on Promotion and Demotion of Domain Controllers is to not support it. If the server is already a domain controller, SQL can be installed.  But once SQL has been installed user will  not be permitted to change the DC to a member machine.


BOL : Installing SQL Server on a Domain Controller 2008
• You cannot run SQL Server services on a domain controller under a local service account or a network service account.
• After SQL Server is installed on a computer, you cannot change the computer from a domain member to a domain controller. You must uninstall SQL Server before you change the host computer to a domain controller.
• After SQL Server is installed on a computer, you cannot change the computer from a domain controller to a domain member. You must uninstall SQL Server before you change the host computer to a domain member.

 
For more information:
- Installing SQL Server on a Domain Controller 
You may encounter problems when installing SQL Server on a domain controller 
Error message when you install SQL Server 2005 on a Windows Server 2008-based RODC: "Failure creating local group SQLServer2005SQLBrowserUser$<ServerName>"
- Best practices that you can use to set up domain groups and solutions to problems that may occur when you set up a domain group when you install a SQL Server 2005 failover cluster


For the SQL Engine, Analysis Services, SQL Browser, you should also check the SPN's in the active directory.
 

 

Michel Degremont | Premier Field Engineer - SQL Server Core Engineer |