Online SNIA Dictionary

ACS [Permalink]

Acronym for Automated Cartridge System.

alternate client restore [Permalink]

The process of restoring files to a different client than the one from which they were backed up.

alternate path restore [Permalink]

The process of restoring files to a different directory than the one from which they were backed up.

Automated Cartridge System [Permalink]

Synonym for tape cartridge handling robot.

automatic backup [Permalink]

A backup triggered by an event (e.g., a schedule point, or a threshold reached) rather than by human action.

backup [Permalink]

1. A collection of data stored on (usually removable) non-volatile storage media for purposes of recovery in case the original copy of data is lost or becomes inaccessible; also called a backup copy or replica.

To be useful for recovery, a backup must be made by copying the source data image when it is in a consistent state.

2. The act of creating a backup. See archive.

backup client [Permalink]

A computer system containing online data to be backed up.

backup copy [Permalink]

A collection of data stored on (usually removable) non-volatile storage media for purposes of recovery in case the original copy of data is lost or becomes inaccessible; also called a backup or replica.

backup manager [Permalink]

An application program whose purpose is to schedule and manage backup operations.

backup policy [Permalink]

Rules for how and when backup should be performed.

The policy includes which data is to be backed up, the schedule on which backups should occur, which devices and media are eligible to receive the backups, how many copies are to be made, and actions to be performed if a backup does not succeed.

Backup to Disk (B2D) [Permalink]

Backup onto disk drive(s).

Backup to Tape (B2T) [Permalink]

Backup onto tape media.

backup window [Permalink]

An interval of time during which a set of data can be backed up without affecting applications that use the data.

carousel [Permalink]

A library or a component of a library in which the media are stored in and selected from a rotating assembly.

catalog [Permalink]

1. [Data Recovery] A list of backed up files, directories, and the locations (media identifiers) of the backup copies.

2. [File System] A persistent data structure used by some file systems to keep track of the files they manage.

CDP [Permalink]

Acronym for Continuous Data Protection.

checkpoint [Permalink]

1. [Data Recovery] (noun) The recorded state of an application at an instant of time, including data, in-memory variables, program counter, and all other context that would be required to resume application execution from the recorded state.

2. [File System] (verb) An activity of a file system, such as the High Performance File System, (HPFS) or the Andrew File System (AFS), in which cached metadata (data about the structures of the file system) is periodically written to the file system's permanent store, allowing the file system to maintain consistency if an unexpected stop occurs.

cold backup [Permalink]

Synonym for offline backup.

See hot backup, online backup.

Continuous Data Protection (CDP) [Permalink]

A class of mechanisms that continuously capture or track data modifications enabling recovery to previous points in time.

copy on write [Permalink]

A technique for maintaining a point in time copy of a collection of data such that when a logical data location is written, a new physical location is chosen for the existing data, and the existing data is copied to that new physical location.

See pointer remapping.

COW [Permalink]

Abbreviation for copy on write.

cumulative incremental backup [Permalink]

A backup in which all data objects modified since the last full backup are retained as the backup.

To restore data when cumulative incremental backups are in use, only the latest full backup and the latest cumulative incremental backup are required.

See differential incremental backup, full backup.

delta snapshot [Permalink]

A type of point in time copy that preserves the state of data at an instant in time, by storing only those blocks that are different from an already existing full copy of the data.

differential incremental backup [Permalink]

A backup in which data objects modified since the last full backup or incremental backup are copied.

To restore data when differential incremental backups are in use, the newest full backup and all differential backups newer than the newest full backup are required. See cumulative incremental backup, full backup.

Digital Linear Tape (DLT) [Permalink]

A family of tape device and media technologies.

disk image backup [Permalink]

A backup consisting of a copy of each of the blocks comprising a disk's usable storage area.

A disk image backup incorporates no information about the objects contained on the disk beyond what is stored in the image itself, and hence cannot always be used for individual object restoration.

erasure coding [Permalink]

A forward error correction technology used to provide data resiliency and long-term data integrity, by spreading data blocks and parity information across multiple storage devices or systems that may be in multiple physical locations.

Both the level of resiliency and where erasure coding is applied (at the array, at the node, or at the system level) can significantly affect how much processing overhead it consumes.

EVSN [Permalink]

Acronym for External Volume Serial Number.

External Volume Serial Number (EVSN) [Permalink]

A human-readable volume serial number on a removable volume.

FIM [Permalink]

Acronym for Frozen Image Method.

forward error correction (FEC) [Permalink]

A set of algorithms that perform corrections that allow for recovery of one or more bit errors.

frozen image [Permalink]

Synonym for point in time copy.

full backup [Permalink]

A backup in which all of a defined set of data objects are copied, regardless of whether they have been modified since the last backup.

A full backup is the basis from which incremental backups are taken. See cumulative incremental backup, differential incremental backup.

hot backup [Permalink]

Synonym for online backup.

See cold backup, offline backup.

HSM [Permalink]

Acronym for Hierarchical Storage Management.

incremental backup [Permalink]

Any backup in which only data objects modified since the time of some previous backup are copied.

Incremental backup is a collective term for cumulative incremental backups and differential incremental backups. See cumulative incremental backup, differential incremental backup, full backup.

label [Permalink]

An identifier associated with a removable media or cartridge.

Labels may be humanly readable, machine readable, or both. See external volume serial number, media ID.

LAN-free backup [Permalink]

A backup methodology that moves data over a SAN without using LAN resources.

local backup [Permalink]

A backup methodology that utilizes host resources to copy data to a backup location that is under control of the same host.

media ID [Permalink]

A machine-readable identifier written on a removable storage volume that remains constant throughout the volume's life.

See external volume serial number, label.

media manager [Permalink]

A backup software component responsible for tracking the location, contents, and state of removable storage volumes.

network backup [Permalink]

A backup methodology that copies data over a LAN to a Backup Server.

Network Data Management Protocol (NDMP) [Permalink]

A communications protocol that allows data storage devices, robotic library devices, and backup applications to intercommunicate for the purpose of performing backups.

NDMP is an open standard protocol for network-based backup of NAS devices. It allows a network backup application to control the retrieval of data from, and backup of, a server without third-party software. The control and data transfer components of backup and restore are separated. NDMP is intended to support tape drives, but can be extended to address other devices and media in the future. The SNIA has developed a v4 reference implementation, based on donation to it of the original code from NetApp and PDC.

offline backup [Permalink]

A form of backup in which the data being backed up is not accessed by applications for the duration of the backup.

online backup [Permalink]

A form of backup in which the data being backed up may be accessed by applications during the backup.

Online backup of a set of data is usually accomplished through the use of a frozen image of the data.

Operational Recovery (OR) [Permalink]

Recovery of one or more applications and associated data to correct operational problems such as a corrupt database, user error or hardware failure.

OR may use a point in time copy or other techniques that create a consistent set of recoverable data.

OR [Permalink]

Acronym for Operational Recovery.

path length [Permalink]

1. The number of instructions (a rough measure of the amount of time) required by a computer to perform a specific activity, such as I/O request execution.

2. The number of characters in a path name.

point in time copy [Permalink]

A fully usable copy of a defined collection of data that contains an image of the data as it appeared at a single instant in time.

A point in time copy is considered to have logically occurred at that point in time, but implementations may perform part or all of the copy at other times (e.g., via database log replay or rollback) as long as the result is a consistent copy of the data as it appeared at that point in time.

See snapshot copy on write, pointer remapping..

pointer copy [Permalink]

A point in time copy made using the pointer remapping technique.

pointer remapping [Permalink]

A technique for maintaining a point in time copy such that when a logical data location is written, a new physical location is chosen for the updated data, and the pointer for that data is remapped to point to it.

See Copy on Write.

quiesce [Permalink]

To bring a device or an application to a quiescent state.

quiescent state [Permalink]

An application or device state in which (a.) the application or device is able to operate, (b.) all of its data is consistent and stored on non-volatile storage, and (c.) processing has been suspended and there are no tasks in progress; i.e., all tasks have either been completed or not started.

raw partition backup [Permalink]

A bit-by-bit copy of a partition image.

A raw partition backup incorporates no information about the objects contained on the partition, and hence cannot be used for individual object restoration. See disk image backup.

Recorded Volume Serial Number (RVSN) [Permalink]

Synonym for media ID.

recovery [Permalink]

The recreation of a past operational state of an entire application or computing environment.

Recovery is required after an application or computing environment has been destroyed or otherwise rendered unusable. It may include restoration of application data, if that data had been destroyed as well.

Recovery Point Objective (RPO) [Permalink]

The maximum acceptable time period prior to a failure or disaster during which changes to data may be lost as a consequence of recovery.

Data changes preceding the failure or disaster by at least this time period are preserved by recovery. Zero is a valid value and is equivalent to a "zero data loss" requirement.

Recovery Time Objective (RTO) [Permalink]

The maximum acceptable time period required to bring one or more applications and associated data back from an outage to a correct operational state.

replica [Permalink]

1. A general term for a copy of a collection of data. See duplicate, point in time copy, snapshot.

2. An image of data usable by one or more applications without an intermediate restore process.

See backup copy.

replicate [Permalink]

1. A general term for a copy of a collection of data. See duplicate, point in time copy, snapshot.

2. The action of making a replicate as defined above.

restoration [Permalink]

Synonym for recovery.

retention period [Permalink]

1. The length of time that a backup image should be kept.

2. In some file systems, such as that shipped with IBM Corporation's OS/390 operating system, a property of a file that can be used to implement backup and data migration policies.

3. The length of time a compliance volume or file must be maintained undeleted and unchanged.

RPO [Permalink]

Acronym for Recovery Point Objective.

RTO [Permalink]

Acronym for Recovery Time Objective.

RVSN [Permalink]

Acronym for Recorded Volume Serial Number.

serverless backup [Permalink]

A backup methodology that utilizes a device other than the server to copy data without using the LAN.

The copy may be performed by a network-attached controller (e.g., utilizing SCSI Extended Copy), by an appliance within the SAN, or by a Backup Server.

stand alone drive [Permalink]

A removable media drive that is not associated with a media stacker or robot.

third party copy [Permalink]

A technique for performing backups using minimal host resources by copying data directly from the source to the destination without passing through a host.

TPC [Permalink]

Acronym for Third Party Copy.

verify / verification [Permalink]

The object-by-object comparison of the contents of a backup image with the online data objects from which it was made.

versioning [Permalink]

The maintenance of multiple point-in-time copies of a collection of data.

Versioning is used to minimize recovery time by increasing the number of intermediate checkpoints from which an application can be restarted.

volume group [Permalink]

A collection of removable media that reside in a single location, for example in a single robot or group of interconnected robots.

volume pool [Permalink]

A logical collection of removable media designated for a given purpose, for example, for holding the copies of a single repetitive backup job, or for backing up data from a given client or set of clients.

A volume pool is an administrative entity, whereas a volume group is a physical one.

backup window duration [Permalink]

The amount of time required to create a backup.

For example, if a backup uses different resources (storage devices, I/O paths, processing power) than an application, as is common with split mirror point-in-time copies, then the backup window duration is the time required to create the image. If an online backup shares resources with the applications using the data, as is common with copy-on-write point in time copies, the backup window duration may be increased due to resource contention. For an offline backup, the backup window duration is the time during which applications are not allowed to modify the data while the backup operation completes.

split mirror, split mirror copy (split mirror point in time copy) [Permalink]

1. [Storage System] Any of a class of point in time copy implementations or the resulting copies in which the storage for the copy is synchronized to the source of the copy and then split.

A split mirror copy occupies as much storage as the source of the copy.

2. [Data Recovery] A method for generating a frozen image of a set of data.

PIT copy [Permalink]

Abbreviation for point in time copy.