Distributed File Services (DFS) is a service, installed by default with NetWare 6, that provides access to remote volumes. This process, called junctioning, allows volumes to be joined together so that they appear as subdirectories in one file system regardless of their physical location.
A junction is simply a virtual directory or folder that is assigned a pseudo filename within a file system. The junction contains information that redirects file requests to a file system located at the root of another NetWare volume.
Junctions can point to the root of any NetWare 5.1 or 6 traditional or NSS volumes that reside on another server within the same NDS tree. However, a system administrator can create junctions only on NetWare 6 NSS volumes. For a complete list of DFS limitations, see "DFS Limitations " below.
When a junction is created, the Volume Location Database (VLDB) assigns the junction a unique ID, which is automatically stored in the VLDB and also in the corresponding NDS Volume object. When a user views the contents of a junction, the client looks at the unique ID, then queries the database to find the path to the physical volume associated with the unique ID, and then displays the contexts of that physical volume.
In the end, the junction appears to the user as a new subdirectory and its contents include the entire volume that the junction points to. Users are unable to create or manipulate these junctions. The access rights to data within the new volume is still controlled by normal rights assigned to that user on that volume; the junction serves merely as a shortcut to access the volume.
Junctions eliminate the end user's need to know the path to the physical location of the data. For example, if John's data is located on server's X, Y, and Z, you can create junctions on server X that point to all of his data on servers Y and Z. That way, John only has to remember the path to server X, because with junctions, it appears as if the data is all located in one place.
The benefit of this feature is two-fold. Not only does it decrease administration costs by allowing the administrator to move a volume to a different server without making any announcements or having to reeducate users, but it also simplifies the number of paths a user has to remember if his data is located in multiple places on the network.
Before you begin creating junctions, make sure you are familiar with the following DFS limitations:
However, it does support Web-based services, like WebDAV or NetStorage, via the XTier framework or the Microsoft Client via the CIFS protocol.
In order to use DFS to create junctions on your NetWare 6 servers, you must either
Before you can begin to create an actual junction, you must create at least one DFS Management Context at an O or OU level in the NDS tree. You can create more than one Management Context if you have a geographically diverse company. That way, each geographic area can manage and control the junctions and the VLDB Management Service within its own domain.
IMPORTANT: If you are creating more than one Management Context, be aware that a server cannot be a part of two different Management Contexts. If you are junctioning to volumes that are physically located on servers outside your Management Context, and volume repairs need to be made, you will have to contact the network administrator responsible for the Management Context that contains that specific server.
When you create a Management Context, you specify which servers will run the VLDB Management Service and hold the actual database. It is the activated VLDB Management Service, which includes the database, that allows you to create junctions.
Right-click an O or an OU in the NDS tree and then click New > DFS Management Context.
Select one or more servers from the Available list, click the Right-arrow to move them into the Selected list, and then click Next.
The servers that you selected will run the VLDB Management Service and house the VLDB database. Select more than one if you want to keep a copy of the database on another server to prevent data loss or corruption.
Specify where you want to store the database on the server, and then click Finish.
The default location is SYS:\ETC.
Once you create the Management Context, attributes are created in the container object and the service is started on the servers that you selected.
Once the Management Context is created and the VLDB Management Service is up and running, you can create junctions.
In ConsoleOne, create a subdirectory or use an existing subdirectory of any NetWare 6 NSS volume.
IMPORTANT: If you installed a NetWare 6 server within the DFS Management Context after the DFS Management Context has already been activated, you might get an error when you try to create a junction because those NetWare 6 volumes do not have a DFS attribute. To fix this, you must rebuild the VLDB. Follow the instructions in Repairing the Volume Location Database .
Right-click the subdirectory and then click > New > Shortcut > Junction.
You can also create a junction at the root of a volume as well. However, to do this, instead of right-clicking the subdirectory, select the volume and then click the Up-arrow in the ConsoleOne toolbar.
Verify that the NDS tree name is correct, browse to the volume that you are pointing to from the junction, and then click Next.
Name the junction and then click Finish.
To view the newly created junction, from the Console One toolbar, click View > Refresh.
When DFS is activated, it creates the following files in SYS:ETC:
In addition, each NetWare volume will contain a 24 byte, hidden, read-only file called ~DFSINFO.8-P.
IMPORTANT: Do not modify or delete any of these four files. If you accidentally delete any of these files, you must rebuild the VLDB from the VLDB Management Service on the volume that you have deleted the file from to re-create the file. To rebuild the VLDB, follow the instructions in Repairing the Volume Location Database .
Right-click the junction in ConsoleOne.
Click Delete Shortcut > Junction.
Continue with the next section, "Managing the VLDB Management Service ."
To access the VLDB management service, in ConsoleOne, right-click any server that has the VLDB management service running and then click Properties > Supported Services > NSS VLDB.
The management service shows you basic information, such as the version of the service, whether the service is running or not, and the database location.
The management service also allows you to perform the following administrative tasks:
HINT: You can also manage the VLDB Management Service from the server console. To view a listing of the available commands, enter VLDB HELP at the server console.
At this time, to add or remove a replica from a server, you must access the VLDB Management Service from the server that you want to modify.
In ConsoleOne, right-click the server you want to modify, and then click Properties > Supported Services > NSS VLDB.
In the VLDB Management Service, click either Add Replica or Remove Replica.
To start the VLDB Management Service, enter vldb at the server console.
To stop the VLDB Management Service, enter vldb exit at the server console.
You can repair the VLDB in the following three ways:
The repair option restores the last saved copy of your backup files to the database.
You can use this feature only if you have the VLDB Management Service running on more than one server. The VLDB Management Service gets a copy of the database from another server that is currently running the service.
When you rebuild the VLDB, the VLDB Management Service walks the NDS tree, looks at volume and server objects, and then completely rebuilds the database from scratch.