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Using DFS in an Open Enterprise Server 2 Environment

Novell Cool Solutions: AppNote
By Karthik Bachu

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Posted: 10 Oct 2007
 

Contents

Overview:

Novell® Distributed File Services (DFS) for the Novell Storage Services™ (NSS) file system provides location transparency of file data to end users. With DFS, you can create a single virtual file system for data on NSS volumes that spans multiple machines to maximize the use and performance of storage resources.

Dependent Components:

The administrator must install and configure DFS and other OES 2 services that are needed for using DFS on the OES 2 Linux server:

  • Linux User Management
  • NCP Server
  • Novell eDirectory
  • Novell iManager
  • Novell Storage Services (includes DFS)
  • Novell Storage Management Services TM
  • SLP (Service Location Protocol)

SLP Configuration:

SLP DA Configuration:

  • Default Configuration of Open SLP is enough for DFS to work. If the system needs to be configured to use a specific scope and DA, or needs to be configured as a DA itself, then adjustments must be made to the configuration files.

To Configure Default Scope, open /etc/slp.conf file and uncomment

net.slp.isDA = true

Now the Server on which we uncommented above line acts as SLP DA. After modifying the slp file restart rcslpd, using rcslpd restart command.

SLP Client Configuration at Install Time:

Once if we are done with Configuring SLP DA, we can configure slp in other servers as follows.

At SUSE Linux Install time, we get the following Screen.


click for large view

  • Configure NTP if you already have NTP Server running, else select "Use Local Clock only option".

  • Select "Configure SLP to use an existing eDirectory Agent" Radio Button

  • Let Service Location Protocols Scope be DEFAULT

  • Click on ADD and enter the ip of SLP DA Machine [ i.e the machine on which we have configured SLP DA as true ]

  • Click on Next

Configuring SLP on other Servers Post Install:

Edit /etc/slp.conf file and add the following lines at the end of slp.conf file.

net.slp.useScopes = DEFAULT
net.slp.DAAddresses = 10.0.0.1 
net.slp.isBroadcastOnly = false   

Save the file and restart slpd and also smdr.

To start OpenSLP,

rcslpd restart 
rcnovell-smdrd restart

As DFS is tightly dependent on SMS components we require SMDR to be running.

Verifying SMDR Services:

After starting the SLP daemon, test the SLP configuration. Many tools are available to troubleshoot and test the SLP service.

To test OpenSLP, use the command-line tool slptool. The following command is useful:

slptool findsrvs smdr.novell

Output will look like

service:smdr.novell://10.0.0.1:413/linux-78,51600
service:smdr.novell://10.0.0.2:413/linuxT-64,53325
service:smdr.novell://10.0.0.3:413/linuxT-61,53445

Before Doing a Move or Split using DFS, its better to verify with the above command to make sure the source and target servers for the move/split operations are listed. DFS requires SMDR.NOVELL Service running.

DFS Management Context:

Before you create a DFS junction, you must create at least one DFS Management Context at an O or OU level in the Novell eDirectory tree. We will create a DFS Management Context at the O level.

When you create a DFS Management Context, you specify which servers run the VLDB service and hold the actual database.

In iManager Go to Distributed File Services-> Create Management Context

  • Enter Management Context name as name of your O/OU level
  • Enter the name of Replica Site as name any one Server present under that O/OU level
  • Default Database is stored under /var/opt/novell/dfs..
  • Select "Run VLDB Service on Server restart"
  • Click on OK.

This will create the Management Context and start VLDB service on back end. Database used is vdqad. Its mandatory to have a management context before we do a split or move of volumes or data from one Linux server to other Linux server. The status of VLDB can be viewed under Distributed File Services->Manage Replica sites" , it will be in Running State.


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DFS VLDB Services

The Volume Location Database service provides the framework for locating volumes in the management context. Managing the VLDB service involves the creation, day-to-day management, maintenance, and repair of the VLDB.

DFS Junctions

The DFS junction is a special file that takes the place of a directory and its contents. The junction contains information that points to a target location where the data actually resides. The junction can be created at the root of an NSS volume or in any of its directories. The junction can point to the root of the target volume or to any of its directories.

DFS honors the trustees and file system trustee rights that you define for the junction location and target location. You can modify the assigned trustees and their rights at any time after you create the junction. Trustee Users should be LUM enabled Users.

Junctions can be created using iManager, Go to Distributed File Services->Create Junctions link

Enter the Junction name,Source Path and Destination Path. Even we can Modify and Delete Junctions

  • In iManager, click Distributed File Services > Modify Junction.

  • Browse to locate and select the junction you want to manage.

  • On the Junction Properties page, specify the new name/location of the junction.

  • Click OK or Apply to save the change

In the same manner we can even Delete Junction.

Note: If the client is unable to resolve a junction:

  • Check that the VLDB service is running ( use vldb status )

  • Check that the target volume (the one the junction is pointing to ) exists and has not been deleted.

  • Check that the entry for the target volume exists in the vldb.dat file by running vldb list on OES2 Linux. This command does not exist on NW.

  • If the entry does not exist, use vldb repair or vldb add to add it to the database.

DFS Move/Split from Linux to Linux:

Once you have successfully created a Management Context, we can move volumes or split volumes from one server to another server which present under the same tree and same Management Context. Before we do a Move or Split make sure the source and target servers for the move/split operations are listed using the command "slptool findsrvs smdr.novell"

Access iManager, then log in to the eDirectory tree where the server you want to manage resides.

  • In Roles and Tasks, do one of the following: Expand the Storage role to reveal its main tasks.

  • Click on Storage

  • Select the Volume you want to move/split and Click on Move/Split

  • Enter the sub directory name where you want to split the volume ( if you are doing a Split )

  • Enter Target Server name and Volume name and create space for volume using iManager under a new pool or use an existing pool,

  • Once everything is done Click on Finish.

The status of Move/Split can be seen under Distributed File Services->Volume Job Control

The Status of Job will be from Scanning to Running to Updating and then Completed.< There are other states in between ? just not visible because they are over so quickly >If once Split job is Completed,then there occurs

( the original folder is replaced by) a Junction from Source Volume to Target Volume,Using which users can access data on server A without realizing that it is on a different volume on a different server.


click for large view

DFS Move/Split from NetWare to Linux:

Before doing a Move or Split of volumes from netware to Linux OES, we need to enable tsamode to dual on Linux side.

To set the TSAFS mode to dual:

Open a terminal console, then log in as the root user.
At a terminal console prompt, enter

smsconfig -u tsafs			-> Used to Unload TSAFS
smsconfig -l tsafs --tsaMode=dual	-> Used to set to Dual Mode
smsconfig -t				-> Used to list

Reset tsamode to Linux once you are done with Move or Split from NetWare to Linux.

To reset the TSAFS mode to Linux:

Open a terminal console, then log in as the root user.

At a terminal console prompt, enter

smsconfig -l tsafs --tsaMode=linux
smsconfig -t

Note: We cannot do a move / split from NetWare and Linux to the same Linux target server at the same time as we are enabling tsamode.

After Enabling tsamode to dual, the rest of the Move/Split Process is same as Linux to Linux Move/Split Process.

Once Move or Split from NetWare to Linux is done, existing Junctions that were present in NetWare Volumes will work even after the Move

.

DFS VLDB Repair:

The VLDB repair rebuilds the VLDB database. It recursively walks the eDirectory tree down from the management context container, and records information about the Volume objects it discovers in a repair database. On completion, VLDB repair activates the repair database, which replaces the current active database. If there are two replica sites, the other replica automatically gets synchronized to the active repaired database.

Until the repair database is activated, all VLDB requests (that do not explicitly specify that they are referencing the repair database) act against the existing database. Thus, clients can access DFS junctions even while the VLDB is being repaired for those volumes that still have correct entries in the VLDB.

Admin can do a repair by using the command line or iManager:

To use the command line, run

VLDB repair

on the vldb replica server and enter user name and password.

Using iManager:

  • In iManager, select Distributed File Services > Manage Replica Sites.

  • Select the check box next to the VLDB replica site that you want to manage.

  • Select Actions > Repair to open the Repair the VLDB Database page.

  • Select one of the following repair levels, then click OK:

  • Replace the VLDB with Its Last Saved Copy: The repair option restores the last saved copy of the database. It uses the automatically created backup file that it creates whenever it writes out the database.

  • Copy the VLDB from the Context?s Second Replica Site: You can use this feature only if you have the VLDB service running on more than one server. The VLDB service gets a copy of the database from another server that is currently running the service.

  • Rebuild the VLDB by Walking the eDirectory Tree: When you rebuild a database, the VLDB service walks the eDirectory tree, looks at volume and server objects, and then completely rebuilds the database from scratch.

DFS Clients:

DFS Junctions can be accessed using DFS Clients,DFS support is included from the 4.91 Novell client for Windows onwards, however Novell recommends using the latest support pack. NetStorage and CIFS can also be used to access junctions. By mapping the volume using Novell Client we can access the junctions.

Novell Client for Linux 2.0 and Novell Client for Windows Vista Beta 1.0 also supports DFS Junctions.

Conclusion:

Using This AppNote, we can easily configure DFS on OES 2 and we can move or split volumes from one server to another.


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