Resolve a namespace in a distributed file system

In recent years, Microsoft has made many improvements to its Distributed File System (DFS). One of these technologies provides a unified view of File System resources. DFS redirects requests from the UNC Channel again. One of the network drivers maps to the network share where the requested resource is located. The result is that you can add a file server to the network or enhance the existing file server without affecting user access to the file.

The UNC path for redirecting requests to the actual location of the file is the DFS namespace. Essentially, DFS is a unified namespace that presents users with a centralized view of File Server resources. A dfs namespace consists of many parts.

DFS Root

The DFS namespace is essentially hierarchical, and the top is the DFS root. In practice, the root and namespace are considered the same, because the root is often used to refer to the entire namespace. DFS root is a shared file, which must exist in the NTFS Volume.

The DFS root is linked to one or more root targets, while the root target is linked to the UNC share on a file server. The number of root targets that can be linked to a DFS root is determined by the DFS root-related namespace type. The DFS namespace has two types: Independent namespace and domain-based namespace.

The independent namespace stores their configuration information in the host server registry. Information of the domain-based namespace stored in the Active Directory database. This difference affects the number of root targets connected to the DFS root. The independent DFS root can only contain one single root target, while the domain-based DFS root can only contain multiple root targets separated by multiple servers.

Figure 1 below shows a domain-based DFS root. Obviously, this is based on the domain, because the root name \ lab.com \ namespace) reflects the domain name. The central square shows two UNC paths, and both paths are linked to the DFS root like the root target.

Figure 1: DFS root connects to one or more root targets

Files or links in DFS namespaces

The next element in the classification is a file or link as it sometimes points out ). Each file in the DFS namespace is mapped to the Link Target, just as the DFS root is mapped to the root target. The link destination points to a UNC share mapped to a physical folder.

In Figure 2, three file files 1, file 2, and file 3 are defined under the DFS root. Note that I have selected file 1 ). The central window of the console lists the link targets mapped to files.

Figure 2: Each file is mapped to the Link Target.

As you can see, this link is only a UNC channel mapped to the shared file. In addition, in the central window of the console, various information, including the type, path, and submission status, is displayed for the Link Target.

Because a file can be connected to multiple connection targets on different servers, the submission status exists. After this is done, you can create a replication group for the target to be linked, and the replication group will maintain synchronization between various file contents and other files. Figure 3 shows a file with multiple link targets.

Figure 3: Multiple link targets

The submission status of the two link targets is valid ). This means that DFS can specify resource requests to any target. Therefore, if a file server must be repaired offline, the submission status of the server becomes invalid, and DFS stops sending requests to the server until the submission status becomes valid again.

NTFS-level DFS namespace

These factors constitute the DFS namespace. In Figure 4, you can see what the NTFS-level namespace looks like.

Figure 4: DFS content on drive C

Note that the file named Dfsroots is named Namespace ). DFS automatically creates these files when I create the root. The Namespace file is actually shared, but the file system hides the shared file.

Note that there are shortcuts to file 1, file 2, and file 3 under the namespace. These are all target Files specified in the DFS console. At the bottom of the figure is another list of the three folders, which are actually shared files on drive C. The shortcut key I just mentioned maps to these shared folders.