Distributed File System (Microsoft)

Distributed file System (DFS) is a set of client and server services that allow an organization using Microsoft Windows servers to organize many distributed SMB file shares into a distributed file system. DFS provides location transparency (via the namespace component) and redundancy (via the file replication component) 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 unrelated to the DCE Distributed File System, which held the 'DFS' trademark but was discontinued in 2005.

It is also called "MS-DFS" or "MSDFS" in some contexts, e.g. in the Samba user space project.

There is no requirement to use the two components of DFS together; it is perfectly possible to use the logical namespace component without using DFS file replication, and it is perfectly possible to use file replication between servers without combining them into one namespace.

A DFS root can only exist on a server version of Windows (from Windows NT 4.0 and up) and OpenSolaris (in kernel space) or a computer running Samba (in user space.) The Enterprise and Datacenter Editions of Windows Server can host multiple DFS roots on the same server. OpenSolaris intends on supporting multiple DFS roots in "a future project based on Active Directory (AD) domain-based DFS namespaces".

There are two ways of implementing DFS on a server:

Traditional file shares, associated with a single server, have SMB paths of the form

Domain-based DFS file share paths are distinguished by using the domain name in place of the server name, in the form

When a user accesses such a share, either directly or by mapping a drive, their computer will access one of the available servers associated with that share, following rules which can be configured by the network administrator. For example, the default behaviour is that users will access the closest server to them; but this can be overridden to prefer a particular server.

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