Distributed File System (DFS) is a feature of Windows Server that existed in Windows NT 4.0, but didn’t really become useful until the release of Windows Server 2003.
At its simplest, DFS is a technology that allows you to create “virtual file shares” and add what amounts to symlinks or junctions to real file shares to it. So if, for example, you had a situation where you needed to share ten folders off seven different servers, you could instead create a DFS share and create links to the real shares. As far as your end-users are concerned, it’s only the one file share. That way, all users have a “S: drive” with the same folder structure, instead of one group (Finance) having one set of mapped drives and another group (Marketing) having another.
What’s even better is that you can map a DFS link via WAN connection, so people in two different offices can have the same file shares regardless of location. You can also build redundant DFS shares: just create a new share, robocopy the existing data to the new share, then add both shares to your DFS root. That way, if you ever need to take one of those servers offline, end users will still be able to access the data. In fact, they shouldn’t even notice a difference!
Although DFS was created for corporate customers, I have found one neat use for it at home. As you might know, I got a new computer for Christmas. That computer runs Windows Vista Home Premium; it therefore cannot join my local SBS 2003 domain, which has around 8 total shared folders. As you might also know, Windows networking has always been pretty crappy. After a week of owning the new computer I got sick of getting the dreaded “multiple connections to the same server using more than one set of credentials are prohibited” error with all the different file shares (even though I was only using my domain username and password). I therefore went in and created a DFS share for my local domain. I now map the DFS share as a drive, and Windows only asks me for credentials when I first map it – from that point on it’s smooth sailing!
Learn everything you could ever want to know about DFS here.