A question often asked when discussing an Active Directory design: “Don’t we need an enterprise OS for our domain controllers?”. This question is mostly asked when thinking about hosting one or more additional DFS namespaces on the domain controllers. The answer is fairly simple:

With a Windows 2008 R2 Standard SKU you can create the following namespaces:

• 1 standalone namespace (http://www.microsoft.com/windowsserver2008/en/us/r2-compare-roles.aspx)
• Multiple domain based namespaces

With a Windows 2008 R2 Enterprise SKU on the other hand you can create:

• Multiple standalone namespaces
• Multiple domain based namespaces

An example on a Standard SKU, I created several domain based and one standalone:

After trying to create an other standalone namespace:

One of the differences between standalone and domain based namespaces is how you access them:

• Standalone: \\server\dfsnamespaceofchoice
• Domain: \\domain.tld\dfsnamespaceofchoice

In my opinion it doesn’t really make sense to create a standalone namespace on a domain controller. Creating such a namespace on of your domain controllers makes that DC “special”. I don’t like “special” –don’t reboot that DC – domain controllers. Above that if you want the standalone namespace to be high available you need to cluster it. Again domain controllers should not reside on cluster nodes.

An other point: domain based namespaces don’t have to be hosted on domain controllers. They can, but it’s not a must. All you have to keep in mind is that you have to add multiple name servers yourself. This won’t happen automagically.

In the past the above wasn’t always like that. Somewhere in the past this was changed for Windows 2003: http://support.microsoft.com/default.aspx?scid=kb;en-us;903651

So to conclude: if you aren’t going to host standalone namespaces on your DC’s, you do not need a enterprise OS for the DFS part.