Reviewing DFS Terminology
Updated: March 28, 2003
Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2
If you are not familiar with DFS, review the following terms and definitions to understand the important elements of a DFS configuration. For visual examples of these concepts, see Figure 2.4 through Figure 2.7 later in this section.
DFS namespace A virtual view of shared folders on different servers as provided by DFS. A DFS namespace consists of a root and many links and targets. The namespace starts with a root that maps to one or more root targets. Below the root are links that map to their own targets.
DFS root The starting point of the DFS namespace. The root is often used to refer to the namespace as a whole. A root maps to one or more root targets, each of which corresponds to a shared folder on a separate server. The DFS root must reside on an NTFS volume. A DFS root has one of the following formats: \\servername\rootname or \\domainname\rootname.
Root target A physical server that hosts a DFS namespace. A domain-based DFS root can have multiple root targets, whereas a stand-alone DFS root can only have one root target.
Stand-alone DFS namespace A DFS namespace whose configuration information is stored locally in the registry of the host server. The path to access the root or a link starts with the host server name. A stand-alone DFS root has only one root target. Stand-alone roots are not fault tolerant; when the root target is unavailable, the entire DFS namespace is inaccessible. You can make stand-alone DFS roots fault tolerant by creating them on clustered file servers.
Domain-based DFS namespace A DFS namespace that has configuration information stored in Active Directory. The path to access the root or a link starts with the host domain name. A domain-based DFS root can have multiple root targets, which offers fault tolerance and load sharing at the root level.
DFS path Any Universal Naming Convention (UNC) path that starts with a DFS root.
Link A component in a DFS path that lies below the root and maps to one or more link targets.
Link target The mapping destination of a link. A link target can be any UNC path. For example, a link target could be a shared folder or another DFS path.
Figure 2.4 illustrates the elements of a stand-alone DFS namespace in the Distributed File System snap-in. These elements include a stand-alone DFS root, a single root target, and multiple links.
Figure 2.4 Elements of a Stand-Alone DFS Namespace
Figure 2.5 illustrates the elements of a domain-based DFS namespace in the Distributed File System snap-in. Notice that the \\Reskit.com\Public root has two root targets on different servers.
Figure 2.5 Elements of a Domain-based DFS Namespace
Figure 2.6 illustrates multiple link targets for the Software link. Notice that the link targets exist on three different servers and that the administrator has disabled referrals to the link target on \\dfs-03. DFS will not refer clients to the link target on \\dfs-03 until the administrator enables referrals.
Figure 2.6 Multiple Link Targets
The roots and links displayed in the Distributed File System snap-in also appear on each root server’s local storage as follows:
When you create a DFS root, you specify a shared folder to use as the root folder. If you add multiple root targets to a domain-based DFS root, you specify a shared folder on each of those root targets. (The shared folder names should always match the root name.)
When you add links to the root, DFS creates special folders under each root folder. These folders, called link folders, are actually reparse points, and they display the following error message if you try to access them on the local server:
E:\Public\GroupData is not accessible. The network location cannot be reached.
Users who access the link folders from across the network are redirected to the appropriate link target.
Figure 2.7 illustrates volume E:\ on the local storage of one of the root targets. The volume contains root and link folders for the \\Reskit.com\Public namespace.
Figure 2.7 Root and Link Folders