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The most recent version of this material is maintained on the ITSO Internet Web pages at:

http://www.redbooks.ibm.com/solutions/systemsmanagement/tsm/c_afsdfs.html

Today, businesses work in a global marketplace without time and geographic boundaries. International collaboration, Internet commerce, a mobile workforce, and scarce resources are today's realities. The tie that binds this globally scattered business infrastructure is shared information. To remain competitive in the global marketplace, a company's access to this information must be fast and direct, regardless of where the information is stored or where it is being delivered.

As a result, seamless, convenient, secure shared access to information has never been more critical to supporting the business goals of an organization.

IBM and its Transarc subsidiary offer two enterprise file system products—AFS and DFS—that provide a single, shared file space to all authorized users from all possible locations. The file-sharing domain is no longer defined by specific organizations, locations, types of machines or network configurations. With enterprise file systems, heterogeneous server and client machines can be joined together into a global, shared information system. Such an environment provides access to files from multiple heterogeneous platform servers supporting

applications, regardless of the location of the file or the end user.

Wherever key information resides and wherever it is needed, AFS and DFS enable the user to access all the information in the enterprise file system, using standard, unmodified, pre-existing applications such as word processors, presentation and publication packages, engineering tools and workflow applications. By seamlessly integrating with these applications, enterprise file systems transform a network of computers into the unified productive workspace required for the global information age.

14.1 Andrew File System

Andrew File System (AFS), the original enterprise file system product from Transarc, has its origins in Carnegie Mellon University's (CMU) Andrew Project.

AFS was initially developed to provide central management and storage for file resources across an entire university campus. This environment consisted of hundreds or thousands of heterogeneous workstations used by students and faculty, who needed to share data regardless of which system they were using. In 1989, members of the original design team founded Transarc and

commercialized this technology to become AFS.

AFS has since seen widespread success at over 400 worldwide organizations which are using AFS to provide information to over two million end-users and tens of millions of users through the Web. Commonly supported applications include internal publication of reports, policies and procedures, as well as shared workspace for scientific collaboration and software design. AFS is also commonly used to support other large workgroup functions and for software distribution.

Furthermore, AFS has also proven to be an excellent infrastructure for highly available World Wide Web content hosting.

AFS is designed for medium-sized businesses and large departments within a corporation that need a scalable, high-performance, reliable distributed file sharing system. AFS provides robust security and an easy-to-use administrative model for file sharing that supports broad platform coverage on UNIX (IBM AIX, Sun Solaris, Sun OS, HP-UX, SGI-IRIX and Digital UNIX), Windows (NT, 95 and 98), and additional desktop platforms such as Macintosh and Netware.

14.2 Distributed File System

Distributed File System (DFS) has its origins in AFS, and was developed as part of the Open Software Foundation (OSF) Distributed Computing Environment (DCE) in the early 1990's. DCE and DFS were the outcome of the OSF's multi-vendor, cooperative initiative to create a set of standard components for distributed computing environments.

DFS has also seen widespread success, within more than 200 worldwide organizations using DFS to provide information to more than one million

end-users and to tens of millions of users through the Web. Commonly supported applications are large scale general purpose file sharing within government agencies and global enterprises, Effective Engineering Collaboration within aerospace, electronic and automotive corporations, and Highly Available Web Content Hosting Systems within financial services organizations providing Web-based securities trading and online service offerings.

DFS is designed for tightly integrated enterprise applications where a standard infrastructure, such as DCE or other DCE-enabled applications like IBM's TXSeries Encina API, IBM's Global Sign-On, or IntelliSoft's SnareWorks, are of interest. DFS supports global enterprises and large organizations with enterprise file sharing across the mainframe (OS/390), UNIX (IBM AIX, Sun Solaris and HP-UX), Windows (NT, 95, and 98), and additional desktop platforms, such as Macintosh, Netware, and OS/2. DFS uses the industry-standard DCE security, naming, and remote procedure call (RPC) for its distributed computing

infrastructure.

14.3 Tivoli Storage Manager backup support for AFS and DFS

The Tivoli Storage Manager AIX backup-archive client includes support for both AFS and DFS.

The Tivoli Storage Manager AIX AFS/DFS backup support system includes:

• AFS file backup client programs (command line and GUI)

• DFS file backup client programs (command line and GUI)

• AFS volume agent programs

• DFS file set agent programs

The AFS file backup client and the DFS file backup client allow users to back up or restore either AFS or DFS files and directories, as well as the AFS and DFS access control lists (ACLs) for directories, including the additional mount point support. Full support of ACLs means that users backing up data using the backup/archive GUI or the backup/archive command line have all ACLs backed up for possible future restoration. This helps ensure that access privileges are maintained as they were before the failure. Tivoli Storage Manager provides

recognition and appropriate handling of mount points. Its ability to exclude unwanted file systems and directories allows Tivoli Storage Manager users to avoid scanning entire DFS directory trees needlessly.

By specifying variable virtual mount points, Tivoli Storage Manager makes it possible to designate many virtual mount points with only one virtual mount point statement. This eliminates the overhead costs that could be accrued by

potentially thousands of virtual mount points having to be processed individually.

The AFS volume backup to Tivoli Storage Manager and the DFS file set backup to Tivoli Storage Manager consist of an interface program between either AFS or DFS backup commands and a Tivoli Storage Manager server, to backup and restore AFS or DFS data. The interface program is a fully integrated part of the backup mechanism and uses Tivoli Storage Manager API function calls to perform these tasks. This means that each phase within the backup process can be run in parallel. Tivoli Storage Manager then buffers these multiple "tasks" to disk and migrates the data to tape at high speed, which dramatically decreases the time required to complete backup.

The AFS volume backup agent stores AFS data by volume. The DFS file set backup agent stores DFS data by file set. Through the Tivoli Storage Manager API, each full or incremental volume dump or file set dump is sent to a Tivoli Storage Manager server as a file with the same name as that of the volume or file set. The volume dump files or the file set dump files associated with a dump are stored in a single file space in Tivoli Storage Manager storage called the dump ID string. A Tivoli Storage Manager administrator can delete an AFS or DFS backup dump from Tivoli Storage Manager storage by deleting the file space in which it is stored.

14.3.1 Key features

Tivoli Storage Manager AFS/DFS backup client system support consists of the following programs:

• AFS file backup GUI and command-line clients

• DFS file backup GUI and command-line clients

• AFS volume backup agent

• DFS fileset backup agent

Each program is described in more detail in the following manuals:Tivoli Storage Manager Using the UNIX Backup-Archive Clients, SH26-4105, andTivoli Storage Manager AFS/DFS Backup Clients,SH26-4106.

14.3.2 The BUTC and BUTA backup programs

Transarc's AFS backup commands back up AFS volumes to tape devices using the BackUp Tape Coordinator (BUTC) program that prompts for the tapes to which it writes the backup data. Each machine running BUTC is connected to a tape device that can be a simple drive or a stacker.

The Tivoli Storage Manager agent program, BUTA (which was originally derived fromBack Up To ADSM), is a replacement for BUTC, the tape interface program of the volume backup system. The AFS/DFS BUTA program is an interface between the AFS/DFS backup commands and a Tivoli Storage Manager server, and lets you back up and restore AFS data by volume and DFS data by fileset.

AFS/DFS BUTA accomplishes these tasks using Tivoli Storage Manager

application programming interface (API) function calls. Through the Tivoli Storage Manager API, each full or incremental volume dump is sent to a Tivoli Storage Manager server as a file with the same name as that of the volume.

14.4 Benefits of using the AFS/DFS BUTA programs

The AFS/DFS BUTA programs offer several benefits over using Transarc's BUTC program to back up or restore volumes/filesets. Table 9 compares the

characteristics of the BUTC and the BUTA programs.

Table 9. Comparing the BUTC and the BUTA programs

Characteristics of BUTC Characteristics of BUTA Each BUTC instance requires a tape device.

It is not always practical to run BUTC on each file server.

The BUTA program provides a single point of control through the Tivoli Storage Manager server for all tapes.

There is no disk buffering. Disk buffering permits multiple incoming buta streams per tape drive.

It is not practical to use high-performance tape libraries.

The number of BUTA instances you start is limited only by the network constraints, thereby providing the possibility of increased performance.

You can create backup copies using the Tivoli Storage Manager copy storage pool function.