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This chapter presents some basic concepts and terminology used when referring to backup operations in a networked environment,and further defines those concepts and how they are used in BACKUP.UNET.
If you are familiar with the concepts involved with backing up and restoring data, you may want to skip the initial sections and begin with System Overview on page 2-5.
BACKUP.UNET backs up files and directories in a networked UNIX system environment. This section explains a few of the terms and concepts used in a network.
A network is a collection of interconnected computer systems that share information, hardware, and software (see Figure 2-1.) Networks let users on one machine access data or devices on another machine across the hall or across the country.
Being on a network allows you to take advantage of the processing capabilities available on the large mainframe computers, mini computers, and individual workstations that are part of that network.
Graphic: Figure 2-1.
Because data shared and generated on a network can be extremely critical, it is important to be able to save this information. If the data is lost, destroyed or corrupted, it must be restored.
However, just saving all that important data can be a job of truly immense proportions. For just one machine, keeping track of what media is used to store the data, where that media is kept, which media have information on them that can be of use, is enough to make storing the data very complex. For a whole network of machines, this job can be next to impossible.
Using BACKUP.UNET, you can back up and restore files and directories from any source on the network to a designated device that is also part of the network.
Network protocols are the rules that control how the machines on a network communicate with each other. These protocols are necessary for data transmission and reception, and define the interfaces between the machines and the communication or transport media (for example, Ethernet and TCP/IP).
A local area network (LAN) is a data communications network connecting computers, printers, terminals, workstations, and other devices in a given geographical area. The area might be a specific floor, an entire building, a group of buildings, or even a university campus.
Your LAN may include a number of different hardware devices all running a UNIX operating system. BACKUP.UNET allows you to back up and restore files and directories on your network safely, efficiently, and easily.
Distributed file systems make files in the file systems of other machines appear to be part of the file system in your own machine. Programs access these remote files in the same way they access local files; this means that programs do not have to be modified or include special processing to access these remote files.
Distributed file systems provide two benefits:
BACKUP.UNET is able to backup and restore files on remotely mounted file systems as easily as local files.
BACKUP.UNET does not need a distributed file system to operate. Additionally, the network service features of BACKUP.UNET provide the capability to deal with the large amounts of data that are commonly found in network installations.
Network systems or hosts are said to be participating if they either provide or use BACKUP.UNET services.
All of the participating systems in a single installation are known to each other. All of the systems in your installation need not be of the same make or type; however, each must be running a version of the UNIX operating system that has a compatible network interface.
For example, a BACKUP.UNET component running on a Sun workstation is able to use the services of another BACKUP.UNET component running on a DEC VAXTM machine.
BACKUP.UNET is made up of several different components. These components are discussed in the following paragraphs.
A system host is a participating computer that provides and/or uses BACKUP.UNET services. Each host has a backup/restore processor (BRP) or an I/O provider (IOP) installed on it; it may have both. This host can also be designated as a syncro-server, a special host type that is responsible for synchronizing the system-wide tables used by BACKUP.UNET.
All BACKUP.UNET hosts report their own status in a log file; certain designated machines also receive and maintain a log file containing status information from other hosts in the BACKUP.UNET system. These machines are designated as reporting hosts. HEADING3Backup/Restore Processor
A participating host that performs backup and restore operations has a BACKUP.UNET component called the backup/restore processor (BRP). The BRP is a server daemon that allows both backup and restore operations to be initiated locally or remotely (from another host). The BRP maintains the host system's backup data information, performs full and incremental backups, and responds to requests for file restores. HEADING3I/O Provider
A participating host with I/O devices, which is used remotely or locally by other BACKUP.UNET components, has an I/O Provider (IOP) daemon running on it. The IOP responds to requests from BRPs, running locally or on other hosts, for tape mounts and read or write operations. HEADING3Syncro-Server
A participating host that is designated as a BRP and/or an IOP can also be designated as a syncro server. A syncro server host maintains and updates the BACKUP.UNET global database tables so that they are the same on every host; ensuring that each host has a consistent image of the BACKUP.UNET environment.
Each time a backup is run, BACKUP.UNET generates catalog entries, available network wide, that show the storage location of all backed up files and directories. This makes it easier to find the files that need to be restored. These catalog entries are part of the BACKUP.UNET database which is automatically backed up as part of each backup operation.
BACKUP.UNET reads the files and backs them up to the backup media. Depending on how much data was backed up in a particular backup operation, there may be only one volume, or there may be several volumes. All backup volumes are automatically managed by BACKUP.UNET.
A backup volume is a single volume, for example a 9 track tape, a cartridge tape, or an 8mm cartridge tape, that has been labelled by BACKUP.UNET. This type of label is created electronically at the beginning of the tape, and identifies and describes the data recorded on the tape. The volume's label protects it from being inadvertently overwritten by BACKUP.UNET.
Each BACKUP.UNET volume has a record in the volume table. In addition to the label, the volume table records how many blocks of a volume have been used and how many backup segments are on it.
Backup segments are created by using the append feature during backups. The append feature allows several host systems to be backed up to a single tape volume. It also allows a host to put a series of backups (for example, a single full backup and subsequent incremental backups) on one tape volume.
Note: Only 9 track, 8mm, 4mm (DAT), and some TK 50 devices can support the append feature.
During the first backup, the backup data is written to a BACKUP.UNET labeled tape (a tape that does not contain any backup data) followed by three tape marks (end of file or EOF marks). When the backup is complete, the tape contains a backup segment (the backed up data) and three tape marks.
When the second backup is started, BACKUP.UNET skips forward one segment, skips one tape mark, writes a tape mark, writes the second segment (the second backup's data), and writes three tape marks. The tape now contains the first segment, two tape marks, the second segment, and three tape marks. The process continues for each subsequent appended backup.
A backup media pool is a collection of volumes, such as tapes or removable disks, used specifically for backup purposes by BACKUP.UNET. Each media pool contains the same type of media; for example, one pool could contain 8mm tapes while another pool could contain TK 50 tapes. Once you have defined a media pool, its backup volumes may be used by machines in a central location (for example, in a computer room) or by machines at remote locations.
The BACKUP.UNET media pools are managed by an IOP. Each IOP has one or more media pools assigned to it; media pool assignment, by IOP, is known to all participating systems so that any BRPs in your installation can use any media pool. There should be at least one media pool associated with each IOP, or a single media pool may be assigned to more than one IOP.
Producing a backup that can be used in the event you need to restore your entire file system may depend on factors such as selecting the right files and backup options, and the quality of the backup media. Use only high quality tapes that are compatible with your tape drives.
Label backup volumes clearly and store them in a secure place. The type of information that should be included in a label is as follows:
Figure 2 2 shows a sample backup volume label.
Graphic: Figure 2-2. Sample Backup Volume Label
Reusing backup volumes for subsequent backups is called recycling. Backup volumes should not be recycled indefinitely. With repeated use tapes will eventually wear out.
You must decide how long to store backed up data before recycling or reusing the backup volumes. The goal is to provide maximum data security while using the least amount of storage media. To help manage a recycling schedule, BACKUP.UNET allows you to automate a schedule for recycling backup media.
BACKUP.UNET maintains an online catalog of information about files that have been backed up. The catalog allows BACKUP.UNET to track and locate which files have been backed up, when, and on what volumes. When a file restore operation is requested, you can query the catalog to locate the exact volume on which the file was backed up.
Files backed up with BACKUP.UNET can also be restored using BACKUP.UNET. By default, files are restored from the most recent backup, but can be restored from any backup you specify. BACKUP.UNET can restore any number of selected files or an entire file system.
Restore options allow you to:
The strength of BACKUP.UNET is its flexibility. How it performs backups and restores is the key to its value. The following paragraphs describe the steps involved during a backup and a restore.
The steps illustrated in Figure 2-3 are performed for each backup operation.
Graphic: Figure 2-3. Steps in the Backup Process
The steps illustrated in Figure 2-5 are performed for each restore operation.
Graphic: Figure 2-5. Steps in the Restore Process
Many ways are available for accessing BACKUP.UNET: using the menu system, entering commands and associated arguments on the system command line, or using the Motif Graphical User Interface (GUI). Access to the menu options, or the ability to execute a specific command or function, depends on your BACKUP.UNET privileges. For more information on privileges, see Chapter 3, Managing Privileges.
The BACKUP.UNET command line interface allows you to enter BACKUP.UNET commands and any corresponding options directly on the command line at the system prompt. You can use the command line interface in addition to the GUI. For information on all of the BACKUP.UNET commands, refer to the BACKUP.UNET Command Reference Guide.
The BACKUP.UNET Graphical User Interface (GUI) is particularly helpful for users who are new to BACKUP.UNET or who have little UNIX experience. The Motif GUI is used in addition to the command line interface, and includes all of the functionality of BACKUP.UNET. The GUI has been designed to be used with a pointing device,usually a three button mouse. All BACKUP.UNET functions and data are displayed inside windows.
For information on using BACKUP.UNET with the Motif GUI, refer to the BACKUP.UNET Motif GUI User's Guide.