Distributed File System (Microsoft)

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This article is about Microsoft's implementation of DFS. For general discussion of the concept and other implementations, see Distributed file system.

Distributed File System, or DFS, is a set of client and server services that allow a large enterprise to organize many distributed SMB file shares into a distributed file system. DFS provides location transparency and redundancy to improve data availability in the face of failure or heavy load by allowing shares in multiple different locations to be logically grouped under one folder, or DFS root.

Microsoft's DFS is referred to interchangeably as 'DFS' and 'Dfs' by Microsoft and is incompatible with the DCE Distributed File System, which held the 'DFS' trademark^[1] but was discontinued in 2005^[2].

1 Details
2 External links
3 References
4 See also

[edit] Details

When users try to access a share that exists off the DFS root, the user is really looking at a DFS link and the DFS server transparently redirects them to the correct file server and share.

A DFS root can only exist on a Windows 2000 or Windows NT 4.0 version that is part of the server family, or on Windows Server 2003. Windows 2000 can only host one DFS root per server, while Windows Server 2003 Enterprise and Datacenter Edition can host multiple DFS roots on the same server. (A Samba server can also host the root of a DFS.)

There are two ways of implementing DFS on Windows 2000 and Windows Server 2003:

Standalone DFS roots allow for a DFS root that exists only on the local computer, and thus does not use Active Directory. A Standalone DFS can only be accessed on the computer which it is created. It doesn't offer any fault tolerance and cannot be linked to any other DFS.
Domain-based DFS roots exist within Active Directory and can have their information distributed to other domain controllers within the domain — this provides fault tolerance to DFS. DFS roots that exist on a domain must be hosted on a domain controller. This is to ensure that links with the same target get all their information replicated over the network. The file and root information is replicated via the Microsoft File Replication Service (FRS).

Windows NT 4.0 only provided Standalone DFS roots, and DFS had to be installed manually, which was available as a free download.

Enhanced DFS management and RDC (Remote differential compression) are part of the "branch office server management" features added to Windows Server 2003 in the R2 release in 2006 ^[3].

Versions 2.6 and later of the Linux kernel come with an SMB client VFS called "cifs" that supports DFS.