Essentially, a DFS namespace is a shared group of network shares residing under a DFS root, which serves as a container for the namespace and performs much the same function for the distributed file system that a root folder serves for a physical volume. In other words, the DFS
root serves as the sharepoint for the distributed file system. Rather than contain subfolders like a root directory does, the DFS root contains links to the shares (local and remote) that form the distributed file system. Each link appears as a subfolder of the root share.
A server that hosts a DFS root is called a host server. You can create root targets on other servers to replicate a DFS namespace and provide redundancy in the event that the host server becomes unavailable. A user can access the DFS root using a UNC pathname in the form \\host server\root name, where host server is the network name for the server hosting the DFS root and root name is the root's name. For example, if you created a root named Shares on a server name FileServer, users would access the DFS namespace from their computers using the UNC pathname \\FileServer\Shares. What they see when they get there is a function of the DFS itself, which might include shares local to that server, shares on other servers, or even shares on the clients' own computers. Users can also specify more highly defined paths, such as\\FileServer\Shares\George\Fil es\Somef i 1 e . doc.
Note If you found yourself limited with Windows 2000 Server's DFS implementation, whereby a host server can host only one DFS root (whether domain or standalone), you'll find more flexibility in Windows Server. DFS in Windows Server now supports multiple standalone and domain roots, giving you greater flexibility in creating and managing roots.
Figure 26-9 illustrates a sample DFS structure. The DFS root is called \ \SRV1\root and contains data in shares from SRV2 and SRV3, program files in a share from APPSRV1, and data from a Windows 98 workstation computer.
Local NTFS folder C:\DFS Root on \\SRV1 shared as \\SRV1\Root
DFS Host Server \\SRV1
Windows XP Workstation \\Fred
Windows XP Workstation \\Fred
DFS Namespace Shared as \\SVR1\Root Figure 26-9: The DFS structure (standalone DFS root)
As illustrated in Figure 26-9, DFS links connect a name in the root to one or more shared folders called targets (called replicas in Windows 2000), or simply DFS shared folders. The links are essentially subcontainers within the root and serve much the same purpose as subdirectories in the root of a physical volume. Within the link object are one or more targets (pointers to shared folders) that define the share that a user sees when the link is opened. The ability to define multiple targets in a given link is what gives DFS its failover capability. DFS responds to a client request with the list of all targets in a requested link. The client then decides which one to use. If any particular target (share) referenced in a link is unavailable (the server sharing it is offline or times out, for example), the client can use a different one.
Tip Although you might assume that each replica associated with a particular link will be a copy of the same folder, that isn't the case. DFS doesn't provide any replication of data between / replicas by default. Nothing prevents you from defining multiple replicas in a DFS link, each pointing to completely different content. This presents interesting options for creating dynamic content on Web sites that use DFS in their underlying structure. Provide a means of replication and synchronization if you need to ensure that the content in the multiple replicas is identical. See the section "Replication" later in this chapter for more information.
Was this article helpful?