One of the many interesting new features in Windows Server 2008 is the Read Only Domain Controller (RODC). Simply put , the RODC can only be updated by another Domain Controller i.e. NOT directly. It is designed for the branch office and caches the credentials of the users in that branch and saves users then having to round trip to the main domain controllers back at head office. This really comes into when the link to Head office breaks as the local users can still login using the RODC.
In the same way these branch offices often need to run SQL Server locally, this might then have replication set back to head office to give maximum local performance when the links to head office are slow and/or unreliable.
There is some debate at the moment about the need for SQL Server 2008 will be supported on Windows Server 2008 when it runs the RODC role.
I am using the word supported here in the Microsoft sense of the word i.e. if it’s broken Microsoft will fix it and support you in the process.
In my opinion SQL Server 2008 needs to be supported on an RODC as you really only want one server in the branch. One way to shoehorn all of a branches applications onto physical server would be to use Hyper-V i.e. to create a virtual machine on top of the physical RODC server with all the application stuff. Virtualising SQL Server in a production environment is a frequently debated topic in its own right, but might work in this scenario as SQL Server is unlikely to be maxed out in this scenario.
So if branch offices figure in your SQL server estate, please let me know what you think about any of this.