Backup3G/User Guide/Glossary

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Revision as of 10:07, 21 April 2006

Active media

A media set containing current backup or archive data.

Active drive

A drive that is being used by a backup or recovery job. The drive is active until the job has completed and has been acknowledged.

Archive

The process of copying (usually inactive) files to a cheaper off-line storage medium. You can have backup3G remove the files from disk after they have been archived. An archive is similar to an at-request backup except that the latter is reusable, while an archive job is defined from scratch.

Appending backup

A backup job whose data is appended to an existing media set that was written by another job.

At-end command

A command that is run at the end of a backup job. Example: send mail warning when a job has failed. See At-unload command.

At-request backup

A manually initiated backup job that is run as required, rather than to a regular schedule.

At-start command

A command that is run before the start of the backup job proper, for example shutting down a database.

At-unload command

An optional command that is run when the backup job is acknowledged to have completed. Example: print the contents of this media set.

Audit trail

The set of log files containing information that is used to verify the correctness of backup jobs.

Automatic backup

A backup job that runs automatically at a set time without operator intervention. Example: an overnight job to back up files in unattended mode.

Backup

A procedure that allows files to be restored from a recent copy in the event of the original being lost or destroyed through accidental deletion, system failure, or some external disaster.

Backup driver

A script that enhances a UNIX backup command to support in a consistent way features such as online indexes and remote backup. FScpio, FSdump, FStar and FSfilesys are drivers that are supplied with backup3G. You can use or modify these or write your own.

Backup item

The ‘what’ and ‘how’ of a backup. An item comprises the name of an object (that is, a directory or filesystem) to be backed up, the backup method, and whether an online index will be created. Thus a directory name can appear in several backup items, so that you have the choice of using different backup methods. Item details also include the host name, so that duplicate directory names on different machines can be distinguished. An item can have a blank directory name; see Nonbackup item.

Backup job

A collection of backup steps which are intended to write to the same device in sequence. The job information includes the drive name, the run time, and the order in which the steps will be run.

Backup media

Specifically, storage media used for backups. Generally, any removable storage medium such as magnetic tape, diskette or optical media.

Backup method

A standard method of doing a backup. This consists of:

• the actual command that will do the backup
• the format (e.g. cpio, dump, tar)
• details of support for extended facilities such as online indexes, multi-part backups and remote backups.

Backup3G comes with several standard backup methods. You can define new methods specific to your site.

Backup step

An occurrence of an item in a backup job. The list of steps in a backup job is the list of items to be backed up and the order in which they will be run.

Base directory

The top-level filesystem or directory that is backed up in a backup step.

Capability

A capability is the ability to use a backup3G feature or menu option. Backup3G users have one or more capabilities, which define the parts of backup3G they can access. For example, to recover files you need the recoverALL or recover capability. backup3G doesn’t show options that you don’t have the capability to use. See also Role.

Current set

A group of backup jobs intended to be written to a single media set.

Device

The UNIX device file name for a drive—e.g. /dev/tape, /dev/rfd0. For tape drives, both the ‘rewind on close’ device name and the ‘no-rewind’ device should be specified. For character devices the raw device name should be used—for example /dev/rfd0, rather than /dev/fd0.

Drive

A tape or diskette drive that can be used to read or write backup data.

Drive host

For a remote backup, the machine to which the backup drive is attached.

Drive operations

A set of commands or functions which can be performed to manipulate media in a drive—e.g. skipping past N files, rewinding and unloading a tape, checking drive status, etc. Commonly, a set of drive operations equates to an operating systemspecific set of commands, such as the mt command found on many UNIX systems.

End-of-data marker

A short file written after the last data file in a media set. backup3G scans for this marker before appending a new backup to an existing media set, to avoid the possibility of overwriting live data.

Expired media set

A media set containing backup or archive data that has passed its expiry date. The data is still stored but the volumes in the set are available to be used by another job.

Expiry

date The end of the retention period for a backup job. After this date, the media set become available to be used by another backup job. A null expiry date means that the volume will never expire automatically.

File host

For a remote backup, the machine on which the files to be backed up are stored.

If not done

Flag that determines what should happen when a scheduled backup job is not run by the end of the scheduled time period. ‘Abandon’ removes the job from the list of outstanding backups. ‘Outstanding’ leaves the job on the list of outstanding backups.

Image copy; A direct copy of a raw disk partition or large single file.

Index/Online index

A compressed index that lists information about backed-up files. Indexes can be browsed and used to select files to be recovered. As indexes may take up large amounts of disk space, they can be enabled or disabled for any backup item.

Job set

A group of backup jobs intended to be written to a single media set.

Jukebox

A device for automatically loading tapes into a drive. A jukebox can randomly access slots (unlike so-called ‘dumb’ stackers, which simply load the tape from the next slot in sequence). Larger jukeboxes comprise one or more self-contained drives with an internal library of tapes or optical disks. Jukeboxes are supported through the COSstacker module.

Label

The backup3G media database uses a unique number to logically keep track of disks and tapes. Media can be electronically labelled with this number. This provides an extra check that live data are not accidentally overwritten by another backup. The electronic label consists of a short file at the start of a tape (or the end of a diskette), which contains the media number and the date last written.

Label type

The format of the file used to electronically label a tape. backup3G comes with two special label types.

• COSstdtape is a 512-byte file at the start of a tape, containing the media number and date last written.
• end_label writes the label at the end of a floppy disk or other seekable device, to prevent it from being overwritten.

Load area

A staging area or location such as a trolley, from which media can be manually loaded into a drive. For example several scratch tapes can be allocated from the main media library to a trolley, and used in backup jobs over the next few days.

Load class

The class of operations or commands used to load and unload media. Backup3G comes with several standard load classes, including manual-mt, mc, and dawn.

Load device

A location from which tapes can be automatically loaded into a drive, such as a tape stacker device, jukebox or silo. When tapes are allocated to a load_device, each one is assigned a particular slot number.

Load location

The location of the media that this drive can access. This would usually be a media library, a ‘load device’ such as a jukebox, or a ‘load area’ such as a trolley or other temporary media store.

Load operation

A command used to automatically or manually load or unload media. The standard operations are:

Load

• load the volume from a particular slot in a stacker
• Load_next: load the next volume in sequence
• Unload: unload the volume from the drive.

Load and Load_next are mutually exclusive. Generally Load is only supported by automatic tape libraries or jukeboxes.

Local

host The machine on which the backup job is started.

Log file

The set of progress and status messages for one run of a backup job.

Logical drive name A physical drive unit is defined to backup3G as multiple logical drives if it can: • read and write different media types • be switched among different hosts • is a jukebox containing multiple drives • be loaded both manually and automatically. Media Any type of removable storage media that can be used to write backup data. May include magnetic tape volumes (DAT, DLT, Exabyte, QIC cartridge tape, tape reels), diskettes, and optical media. Media batch Typically, a box of tapes or diskettes bought from one vendor at one time. You can use backup3G’s Media Maintenance and Batch Details facilities to plan media purchases, based on the price and reliability of previous batches. 182 Glossary Media location A location where media may be stored, for example a media library, tape vault or offsite archive. backup3G has facilities to track media movements between locations. A location can also be a temporary staging area from which media may be loaded manually or automatically into a drive for example a trolley, tape stacker device, jukebox or automatic tape library. Media maintenance The physical maintenance procedures that can be carried out on media—e.g. lowlevel format, clean, re-tension, degauss, trim a tape, etc. Media set A multi-volume backup is written to a set of media. Each volume in a set is identified by the Set ID, which is the media number of the first volume in the set, and a sequence number. Media type A unique media format which can be used to read or write data. Examples: “40 GB Digital Linear Tape”, or “3.5 inch 1.44 MB diskette”. One physical drive may support several media types. For example, a cartridge tape drive may support several tape lengths and densities. A media format that is used for different purposes (e.g. multi-part versus single-part backups) can be defined as separate logical media types. Mode The run mode of a backup job specifies how the job can be run. The options, specified during job definition, are: automatic (runs at predefined time without operator intervention), scheduled (runs at a predefined time after being initiated by an operator) or at-request (can be run at any time). Multi-part backup step A backup step that is written over more than one ‘part’ or output file. Example: a single 4.5 GB file that is written in three parts over three 2 GB tapes. Multi-volume backup job A backup job that writes over more than one volume. This could be made up of several single-part backup steps, or one or more multi-part steps or a combination of the two. Non-backup item A backup job step that doesn’t write to the output device. These can be used to do related tasks, such as mounting or unmounting file systems, starting up or shutting down a database, or rewinding a tape. Outstanding backup A scheduled backup that is due to be initiated by an operator. Overdue backup A scheduled backup that has not been initiated by an operator by the end of the scheduled time. Glossary 183 Physical drive name The name of a physical tape or disk drive connected to a computer. Retention period The period during which a media set is guaranteed not to be overwritten by another backup3G job. After this period the volumes are available to be used by another job. Role A role identifies the responsibility for a set of tasks that are shared by a class of users in your organization. Each backup3G user is assigned one or more roles. Each role grants a number of access capabilities, which control what actions the user can perform in backup3G. Run mode Whether the backup job is intended to be run to a regular schedule or only when initiated by an operator. Scheduled backup A backup job that is initiated by an operator and scheduled to start later at a set time and day. On the scheduled day, the backup appears on the operators backup console as an outstanding backup. The operator is prompted to load the tape, then the job starts at the scheduled time. Scheduled backups are typically used to initiate backups that will run unattended on a weekend or overnight. Schedule time The name of a processing cycle. Examples: Daily, Weekly - Friday, Monthly - First Monday. backup3G uses the schedule time to find which scheduled backups are due to be run each day. Scratch pool All the media which are available to be written to. Includes new, unused tapes; tapes that have been marked as scratch; and expired backup and archive tapes. Scratch volume A volume that is available to be written to by a backup job. Slot A slot in an auto-loading device such as a jukebox, where a tape is stored before being loaded automatically into an attached tape drive. Stacker A device for automatically loading tapes into a drive. Stackers simply load the next tape in sequence, unlike jukeboxes, which can randomly access slots. Usage type What a volume is currently used for. Examples: scratch, backup, archive. Uses The number of times a volume has been read or written to. backup3G tries to balance media usage by prompting for the least-recently-used scratch volume of the type required. Volume A single physical unit of storage, such as a cartridge tape, tape reel, or diskette.