Jill over at The Filing Cabinet has a great post this week outlining some new changes coming to DFS (Distributed File System) in Windows Server 2008 (Longhorn). This news comes straight from the DFS Namespaces team at Microsoft, so I'm confident that these features will actually be there in the RTM version of Windows Server 2008.

The biggest new improvement is support for more than 5,000 targets in a domain-based DFS namespace. In Windows Server 2008 you will be able to use the DFS Management snap-in to create a new domain-based namespace in one of two modes:

• Windows 2000 Server Mode: This provides the same DFS functionality and scalability that is currently available in Windows 2000 Server and Windows Server 2003, but running on Windows Server 2008.
• Windows Server 2008 Mode: This new mode provides functionality and scalability, along with support for access-based enumeration (users do not see folders/content that they cannot access).

So far it looks as if these new options in Windows Server 2008 Mode will only be accessible or configurable with Dfsutil, not through the DFS Management snap-in. But the new Windows Server 2008 Mode removes any hard limits that were there from Windows 2000, like the 5,000 target limit. The DFS Namespaces team is currently running performance tests to determine the guidelines and sizing requirements for this new mode.

To be able to create a new domain-based namespace in Windows Server 2008 Mode your servers and domain must have a functional level of Windows Server 2008 (only Windows Server 2008 Domain Controllers). The only other requirement is that all servers hosting the namespace must be running Windows Server 2008, so it looks like you'll need to upgrade all those DFS servers.

One final update to DFS that will probably affect a lot more smaller networks is that stand-alone namespaces hosted on Windows Server 2008 will now support access-based enumeration.