Lesson 5: Configuring Dfs to Gain Access to Network Resources
The Microsoft distributed file system (Dfs) for Windows 2000 Server provides users with convenient access to shared folders that are distributed throughout a network. A single Dfs shared folder serves as an access point to other shared folders in the network. This lesson introduces you to Dfs.
After this lesson, you will be able to
Configure Dfs for Windows 2000 Server to provide user access to shared folders
Estimated lesson time: 40 minutes
The Microsoft Dfs for Windows 2000 Server allows system administrators to make it easy for users to access and manage files that are physically distributed across a network. With Dfs, you can make files distributed across multiple servers appear to users as if they reside in one place on the network.
Dfs organizes shared folders that can reside on different computers, as shown in Figure 10.12. Dfs provides users with easy navigation to these shared folders. Users do not need to know where a resource is on a network to gain access to it. Dfs facilitates administering multiple shared folders.
Figure 10.12 Overview of Dfs
To share file resources across the network, Dfs does the following:
Organizes resources in a hierarchy. Dfs uses a hierarchy of server shares called a Dfs share. To create a Dfs share, you must first create a Dfs root. A Dfs root is a container for files and Dfs links. Each Dfs root can have multiple links beneath it, each of which points to a shared folder. The links of the Dfs root represent shared folders that can be physically located on different file servers. Table 10.9 describes the two types of Dfs roots.
Table 10.9 Types of Dfs Roots
| Type of Dfs Root | Description |
|---|---|
Domain |
Stores the Dfs topology in Active Directory. Allows links to point to multiple identical shared folders for fault tolerance. Supports Domain Name System (DNS), multiple-level Dfs links, and file replication. |
Standalone |
Stores the Dfs topology on a single computer, not in Active Directory. Provides no fault tolerance if the computer that stores the Dfs topology or any of the shared folders that Dfs uses fails. Supports only one level of Dfs links. |
Facilitates network navigation. A user who navigates a Dfs-managed shared folder does not need to know the name of the server on which the folder is shared. This simplifies network access because users no longer need to locate the network server on which a specific resource is located. After connecting to a Dfs root, users can browse and gain access to all resources below the root, regardless of the location of the server on which the resource is located.
Facilitates network administration. Dfs also simplifies network administration. If a server fails, you can move a link from one server to another without users being aware of the change. All that is required to move a link is to modify the Dfs folder to refer to the new server location of the shared folders. Users continue to use the same Dfs path for the link.
Preserves network permissions. A user can gain access to a shared folder through Dfs as long as the user has the required permission to gain access to the shared folder. If further restrictions are necessary, NTFS permissions can be set.
NOTE Only client computers with Dfs client software can gain access to Dfs resources. Computers running Windows NT 4.0 and later or Windows 98 include a Dfs client. You must download and install a Dfs client for Windows 95.
You should consider implementing Dfs if
Users who access shared folders are distributed across a site or sites
Most users require access to multiple shared folders
Server load balancing could be improved by redistributing shared folders
Users require uninterrupted access to shared folders
Your organization has Web sites for either internal or external use
A Dfs topology consists of a Dfs root, one or more Dfs links, and one or more Dfs shared folders (also known as replicas), to which each Dfs link points.
For domain-based Dfs, the domain server on which a Dfs root resides is known as a host server. You can replicate a Dfs root by creating roots on other servers in the domain. This provides file availability if the host server becomes unavailable.
To users, a Dfs topology provides a unified and transparent access to the network resources they need. To system administrators, a Dfs topology is a single DNS namespace. With domain-based Dfs, the DNS names for the Dfs roots resolve to the host servers for the Dfs root.
Because the host server for a domain-based Dfs is a member server within a domain, the Dfs topology is automatically published to Active Directory by default, thus providing synchronization of Dfs topologies across host servers. This in turn provides fault tolerance for the Dfs root and supports optional replication of Dfs shared folders.
The tasks for creating a Dfs are:
Create a Dfs root.
Create a Dfs link.
Add Dfs shared folders (optional).
Set replication policy.
You can create a Dfs root on Windows 2000 FAT or NTFS partitions. However, the FAT file system does not offer the security advantages of NTFS. When setting up a Dfs root, you have the option of establishing either a domain or a standalone Dfs root.
To create a Dfs root
Click Start, point to Programs, point to Administrative Tools, then click Distributed File System.
In the Action menu, click New Dfs Root to start the New Dfs Root Wizard. Table 10.10 describes the wizard options that you can configure.
Table 10.10 Options on the New Dfs Root Wizard
| Option | Description |
|---|---|
Select The Dfs Root Type |
Specifies either a domain or standalone Dfs root. |
Specify The Host Domain |
Specifies the host domain for the domain Dfs root. For The Dfs Root (domain Dfs root type only) |
Specify The Host Server |
Specifies the initial connection point for all For The Dfs Root resources in the Dfs tree or the host server. You can create a Dfs root on any computer running Windows 2000 Server. |
Specify The Dfs Root Share |
Specifies a shared folder to host the Dfs root. You can choose an existing shared folder or create a new share. |
Name The Dfs Root |
Specifies a descriptive name for the Dfs root. |
In a network environment, it might be difficult for users to keep track of the physical locations of shared resources. When you use Dfs, the network and file system structures become transparent to users. This enables you to centralize and optimize access to resources based on a single tree structure. Users can browse the links under a Dfs root without knowing where the referenced resources are physically located.
After you create a Dfs root, you can create Dfs links. Currently, the maximum number of Dfs links that you can assign to a Dfs root is 1000.
To create a Dfs link
Click Start, point to Programs, point to Administrative Tools, then click Distributed File System.
Click the Dfs root to which you will attach a Dfs link. In the Action menu, click New Dfs Link.
In the Create A New Dfs Link dialog box (see Figure 10.13), in the Link Name box, type a name that users will see when they connect to Dfs.
Figure 10.13 Create A New Dfs Link dialog box
In the Send The User To This Shared Folder box type or browse for the UNC name for the actual location of the shared folder to which the link refers.
In the Comment box, type optional additional information to help keep track of the shared folder (for example, the actual name of the shared folder).
In the Clients Cache This Referral For X Seconds box, enter the length of time for which clients cache a referral to a Dfs link. After the referral time expires, a client queries the Dfs server about the location of the link, even if the client has previously established a connection with the link.
Click OK.
The link appears below the Dfs root volume in the Distributed File System console.
For each Dfs link, you can create a set of Dfs shared folders to which the Dfs link points. Within a set of Dfs shared folders, you add the first folder to the set when you create the Dfs link, using the Distributed File System console. Subsequent folders are added using the console's Add A New Replica dialog box. The maximum number of Dfs shared folders allowed in a set of shared folders is 32.
When you add Dfs shared folders, you can choose which folders will participate in replication. If you set folders to participate in replication, you must then set the replication policy for the shared folders, described later in this lesson.
To add a Dfs shared folder
Click Start, point to Programs, point to Administrative Tools, then click Distributed File System.
In the Dfs console tree, right-click the Dfs link to which you want to assign a shared folder, then click New Replica.
In the Add A New Replica dialog box (see Figure 10.14), enter or browse for the name of the new shared folder in the Send The User To This Shared Folder box.
Figure 10.14 Add A New Replica dialog box
In the Replication Policy box
Click Manual Replication to prevent the files located in the folder from participating in replication.
Click Automatic Replication to cause the files located in the folder to participate in replication. Automatic replication is not available for standalone distributed file systems and can only be used for files stored on NTFS volumes on Windows 2000 servers.
Click OK.
You can ensure that the content of folders is always available to users by replicating that content to other roots or Dfs shared folders in the domain. You can replicate both Dfs roots and Dfs shared folders. Replication copies the content of one Dfs root to another, or from one Dfs shared folder to another Dfs shared folder.
Replicating a Dfs root to another server in the domain ensures that if the host server becomes unavailable for any reason, the Dfs associated with that Dfs root is still available to domain users.
To replicate a Dfs root
Click Start, point to Programs, point to Administrative Tools, then click Distributed File System.
In the Dfs console tree, right-click the existing Dfs root that you want to replicate and select New Root Replica.
The New Dfs Root Wizard guides you through the process of replicating the Dfs root.
Setting Replication Policy for Dfs Shared Folders
When replicating a Dfs shared folder, Dfs stores a duplicate copy of the contents of the original shared folder in another shared folder.
Replicating a Dfs shared folder is a two-step process. First, you add the Dfs shared folder to a Dfs link, specifying that the folder will participate in replication. Then, you set the replication policy for the set of Dfs shared folders associated with that link. Replication of Dfs shared folders can be done either manually or automatically, as described in the following sections. Do not mix automatic and manual replication within a set of Dfs shared folders. Using one method of replication exclusively ensures that the contents of the Dfs shared folders remain synchronized.
For domain Dfs roots only, you can enable Dfs to automatically replicate the contents of a Dfs shared folder to other folders in the set of Dfs shared folders. This keeps the content of the Dfs shared folders synchronized as changes to one or more of the Dfs shared folders occurs. Automatic replication is not available for standalone Dfs and can only be used for files stored on NTFS volumes on Windows 2000 servers. Other types of files, such as FAT files, must be replicated manually.
Although invisible to users and administrators, Dfs uses the File Replication Service (FRS) to perform this function. Within a set of Dfs folders, FRS manages updates across any folders that are targeted for replication. By default, FRS synchronizes the contents of the Dfs shared folders at 15-minute intervals.
When you set replication policy, you select one of your Dfs shared folders as the initial master, which then replicates its contents to the other Dfs shared folders in the set of Dfs shared folders.
For domain Dfs, if you do not enable FRS management of Dfs shared folders, you must maintain the same content in all of the Dfs shared folders manually.
To set replication policy for shared folders
Click Start, point to Programs, point to Administrative Tools, then click Distributed File System.
In the Dfs console tree, right-click the Dfs link containing the shared folders for which you want to set a replication policy and select Replication Policy.
In the Replication Policy dialog box (see Figure 10.15), click a Dfs shared folder that you want to use as the master folder for replication, then click Set Master.
Figure 10.15 Replication Policy dialog box
Click each shared folder in the list and click Enable, then click OK.
NOTE Do not mix automatic and manual replication within a set of Dfs shared folders. Using one method of replication exclusively ensures that the contents of the Dfs shared folders remain synchronized.
In this practice you share some existing folders, and create and share some new folders. Then you create a new Dfs root and create some Dfs links.
IMPORTANT To complete the optional procedures in this practice, you must have two computers running Windows 2000 Server. This practice also assumes that one of the two computers is configured as a domain controller and the other computer is configured as a member server in the domain. If you have only one computer, read through the steps in the procedures marked as optional to learn how to perform them in the future.
To share existing folders
Log on to your domain at your domain controller as Administrator.
Start Windows Explorer and share the folders listed in Table 10.12, using all default permissions. You created these folders in Exercise 7 of Lesson 4, earlier in this chapter.
Table 10.12 Shared Folders for Practice
| Folder | Share Name |
|---|---|
C:\Apps\Database |
DB |
C:\Apps\Wordprocessing |
Word |
To create new shared folders on a remote computer (optional)
In Windows Explorer, create the folders listed in Table 10.13 (where C:\ is the name of your system drive) on your second (remote) computer and share them, using all default permissions.
Table 10.13 New Shared Folders for Practice
| Folder | Share Name |
|---|---|
C:\MoreApps\Maintenance |
Maint |
C:\MoreApps\CustomerService |
Custom |
To create a new Dfs root
On your domain controller, click Start, point to Programs, point to Administrative Tools, then click Distributed File System.
The Distributed File System console opens.
On the Action menu, click New Dfs Root.
Windows starts the New Dfs Root Wizard.
Click Next.
The wizard displays the Select The Dfs Root Type page. In this exercise you will create a domain Dfs root.
Click Create A Domain Dfs Root, then click Next.
The wizard displays the Select The Host Domain For The Dfs Root page.
In the Domain Name box, confirm that microsoft.com (or the name of your domain) is displayed, then click Next.
The wizard displays the Specify The Host Server For The Dfs Root page. You will create a Dfs root on your own server.
In the Server Name box, confirm that SERVER1 (or the name of your server) is displayed, then click Next.
The wizard displays the Specify The Dfs Root Share page. Notice that you can use an existing share for the Dfs root, or the wizard can create a new shared folder for you.
In this exercise you will let the wizard create a new shared folder for you. You have to provide both the location of the folder on your computer and a share name.
Select the Create A New Share option. Type c:\app-dfs in the Path To Share box (where C:\ is the name of your system drive), then type Shared Apps in the Share Name box.
Click Next.
The Distributed File System message box appears, asking if you want to create the C:\App-Dfs folder.
Click Yes.
The wizard displays the Name The Dfs Root page. The wizard fills in the Dfs Root Name box for you.
Click Next.
The wizard displays the Completing The New Dfs Root Wizard page, which contains a summary of the choices that you made.
Confirm that the options that the wizard displays are correct, then click Finish.
Notice that the \\microsoft.com\Shared Apps Dfs root now appears in the console tree (where microsoft.com is the name of your domain).
In the following two procedures you will create Dfs links according to Table 10.14 (where C:\ is the name of your system drive).
Table 10.14 Dfs Links for Practice
| Link | Shared Folder | Folder Name |
|---|---|---|
Database |
\\Server1\DB |
C:\Apps\Database |
Word Processing |
\\Server1\Word |
C:\Apps\Wordprocessing |
Maintenance |
\\second_computer\Maint |
C:\MoreApps\Maintenance |
Customer Service |
\\second_computer\Custom |
C:\MoreApps\CustomerService |
To add Dfs links on your domain controller
Open the Distributed File System console and in the console tree, click \\microsoft.com\Shared Apps (where microsoft.com is the name of your domain).
On the Action menu, click New Dfs Link.
The Distributed File System console displays the Create A New Dfs Link dialog box.
Type Database in the Link Name box.
In the Send The User To This Shared Folder box, type \\server1\DB (where Server1 is the name of your domain controller).
Click OK.
Repeat Steps 1 to 5 to add another link called Word Processing, which points to the shared folder \\Server1\Word (where Server1 is the name of your domain controller).
To add a Dfs link to a remote computer
In the console tree, click \\microsoft.com\Shared Apps (where microsoft.com is the name of your domain).
On the Action menu, click New Dfs Link.
The Distributed File System console displays the Create A New Dfs Link dialog box.
Type Maintenance in the Link Name box.
In the Send The User To This Shared Folder box, type \\second_computer\maint (where second_computer is the name of your non-domain-controller computer), then click OK.
Repeat Steps 1 to 4 to add another link called Customer Service, which points to the shared folder \\second_computer\Custom (where second_computer is the name of your non-domain-controller computer).
Close the Distributed File System console.
To gain access to a Dfs root
On your domain controller or your second computer, double-click My Network Places, double-click Entire Network, click the Entire Contents link, double click Microsoft Windows Network, and then double-click Microsoft (where Microsoft is the name of your domain).
Double-click SERVER1.
Windows Explorer displays a list of all shared folders on your domain controller. Notice that one of the shared folders is Shared Apps, your Dfs root.
Does Windows 2000 provide an indication that Shared Apps is a Dfs root and not an ordinary shared folder?
To view the Dfs links, double-click Shared Apps.
Windows Explorer displays the Shared Apps On Server1 window, which shows all the links of Shared Apps.
Does Windows 2000 indicate that the folders inside Shared Apps are Dfs links and not ordinary folders?
Close all open windows.
In this lesson you learned that the Microsoft distributed file system (Dfs) for Windows 2000 Server provides users with convenient access to shared folders that are distributed throughout a network. A Dfs share uses a tree structure containing a root and links. The links of the Dfs root represent shared folders that can be physically located on different file servers.
It might be difficult for users to keep track of the physical locations of shared resources in a network environment. When you use Dfs, the network and file system structures become transparent to users. A user who navigates a Dfs-managed shared folder does not need to know the name of the server on which the folder is shared, or the actual file name.
After connecting to a Dfs root, users can browse and gain access to all resources below the root, regardless of the location of the server on which the resource is located. If a server fails, you can move a link from one server to another without users being aware of the change. All that is required to move a link is a modification of the Dfs folder to refer to the new server location of the shared folders. Users continue to use the same Dfs path for the link.
In the practice portion of this lesson you shared some existing folders, created some new share folders, created a Dfs root, and then created some Dfs links.