Backup Explained

In information technology, a backup, or data backup is a copy of computer data taken and stored elsewhere so that it may be used to restore the original after a data loss event. The verb form, referring to the process of doing so, is "back up", whereas the noun and adjective form is "backup".[1] Backups can be used to recover data after its loss from data deletion or corruption, or to recover data from an earlier time.[2] Backups provide a simple form of disaster recovery; however not all backup systems are able to reconstitute a computer system or other complex configuration such as a computer cluster, active directory server, or database server.[3]

A backup system contains at least one copy of all data considered worth saving. The data storage requirements can be large. An information repository model may be used to provide structure to this storage. There are different types of data storage devices used for copying backups of data that is already in secondary storage onto archive files.[4] [5] There are also different ways these devices can be arranged to provide geographic dispersion,[6] data security, and portability.

Data is selected, extracted, and manipulated for storage. The process can include methods for dealing with live data, including open files, as well as compression, encryption, and de-duplication. Additional techniques apply to enterprise client-server backup. Backup schemes may include dry runs that validate the reliability of the data being backed up. There are limitations[7] and human factors involved in any backup scheme.

Storage

A backup strategy requires an information repository, "a secondary storage space for data"[8] that aggregates backups of data "sources". The repository could be as simple as a list of all backup media (DVDs, etc.) and the dates produced, or could include a computerized index, catalog, or relational database.

The backup data needs to be stored, requiring a backup rotation scheme, which is a system of backing up data to computer media that limits the number of backups of different dates retained separately, by appropriate re-use of the data storage media by overwriting of backups no longer needed. The scheme determines how and when each piece of removable storage is used for a backup operation and how long it is retained once it has backup data stored on it. The 3-2-1 rule can aid in the backup process. It states that there should be at least 3 copies of the data, stored on 2 different types of storage media, and one copy should be kept offsite, in a remote location (this can include cloud storage). 2 or more different media should be used to eliminate data loss due to similar reasons (for example, optical discs may tolerate being underwater while LTO tapes may not, and SSDs cannot fail due to head crashes or damaged spindle motors since they do not have any moving parts, unlike hard drives). An offsite copy protects against fire, theft of physical media (such as tapes or discs) and natural disasters like floods and earthquakes. Physically protected hard drives are an alternative to an offsite copy, but they have limitations like only being able to resist fire for a limited period of time, so an offsite copy still remains as the ideal choice.

Backup methods

Unstructured

An unstructured repository may simply be a stack of tapes, DVD-Rs or external HDDs with minimal information about what was backed up and when. This method is the easiest to implement, but unlikely to achieve a high level of recoverability as it lacks automation.

Full only/System imaging

A repository using this backup method contains complete source data copies taken at one or more specific points in time. Copying system images, this method is frequently used by computer technicians to record known good configurations. However, imaging[9] is generally more useful as a way of deploying a standard configuration to many systems rather than as a tool for making ongoing backups of diverse systems.

Incremental

An incremental backup stores data changed since a reference point in time. Duplicate copies of unchanged data are not copied. Typically a full backup of all files is made once or at infrequent intervals, serving as the reference point for an incremental repository. Subsequently, a number of incremental backups are made after successive time periods. Restores begin with the last full backup and then apply the incrementals.[10] Some backup systems[11] can create a from a series of incrementals, thus providing the equivalent of frequently doing a full backup. When done to modify a single archive file, this speeds restores of recent versions of files.

Near-CDP

Continuous Data Protection (CDP) refers to a backup that instantly saves a copy of every change made to the data. This allows restoration of data to any point in time and is the most comprehensive and advanced data protection.[12] Near-CDP backup applications—often marketed as "CDP"—automatically take incremental backups at a specific interval, for example every 15 minutes, one hour, or 24 hours. They can therefore only allow restores to an interval boundary. Near-CDP backup applications use journaling and are typically based on periodic "snapshots",[13] read-only copies of the data frozen at a particular point in time.

Near-CDP (except for Apple Time Machine)[14] intent-logs every change on the host system,[15] often by saving byte or block-level differences rather than file-level differences. This backup method differs from simple disk mirroring in that it enables a roll-back of the log and thus a restoration of old images of data. Intent-logging allows precautions for the consistency of live data, protecting self-consistent files but requiring applications "be quiesced and made ready for backup."

Near-CDP is more practicable for ordinary personal backup applications, as opposed to true CDP, which must be run in conjunction with a virtual machine[16] [17] or equivalent[18] and is therefore generally used in enterprise client-server backups.

Software may create copies of individual files such as written documents, multimedia projects, or user preferences, to prevent failed write events caused by power outages, operating system crashes, or exhausted disk space, from causing data loss. A common implementation is an appended ".bak" extension to the file name.

Reverse incremental

A Reverse incremental backup method stores a recent archive file "mirror" of the source data and a series of differences between the "mirror" in its current state and its previous states. A reverse incremental backup method starts with a non-image full backup. After the full backup is performed, the system periodically synchronizes the full backup with the live copy, while storing the data necessary to reconstruct older versions. This can either be done using hard links—as Apple Time Machine does, or using binary diffs.

Differential

A differential backup saves only the data that has changed since the last full backup. This means a maximum of two backups from the repository are used to restore the data. However, as time from the last full backup (and thus the accumulated changes in data) increases, so does the time to perform the differential backup. Restoring an entire system requires starting from the most recent full backup and then applying just the last differential backup.

A differential backup copies files that have been created or changed since the last full backup, regardless of whether any other differential backups have been made since, whereas an incremental backup copies files that have been created or changed since the most recent backup of any type (full or incremental). Changes in files may be detected through a more recent date/time of last modification file attribute, and/or changes in file size. Other variations of incremental backup include multi-level incrementals and block-level incrementals that compare parts of files instead of just entire files.

Storage media

Regardless of the repository model that is used, the data has to be copied onto an archive file data storage medium. The medium used is also referred to as the type of backup destination.

Magnetic tape

Magnetic tape was for a long time the most commonly used medium for bulk data storage, backup, archiving, and interchange. It was previously a less expensive option, but this is no longer the case for smaller amounts of data.[19] Tape is a sequential access medium, so the rate of continuously writing or reading data can be very fast. While tape media itself has a low cost per space, tape drives are typically dozens of times as expensive as hard disk drives and optical drives.

Many tape formats have been proprietary or specific to certain markets like mainframes or a particular brand of personal computer. By 2014 LTO had become the primary tape technology.[20] The other remaining viable "super" format is the IBM 3592 (also referred to as the TS11xx series). The Oracle StorageTek T10000 was discontinued in 2016.[21]

Hard disk

The use of hard disk storage has increased over time as it has become progressively cheaper. Hard disks are usually easy to use, widely available, and can be accessed quickly. However, hard disk backups are close-tolerance mechanical devices and may be more easily damaged than tapes, especially while being transported.[22] In the mid-2000s, several drive manufacturers began to produce portable drives employing ramp loading and accelerometer technology (sometimes termed a "shock sensor"),[23] [24] and by 2010 the industry average in drop tests for drives with that technology showed drives remaining intact and working after a 36-inch non-operating drop onto industrial carpeting.[25] Some manufacturers also offer 'ruggedized' portable hard drives, which include a shock-absorbing case around the hard disk, and claim a range of higher drop specifications.[26] [27] Over a period of years the stability of hard disk backups is shorter than that of tape backups.[28]

External hard disks can be connected via local interfaces like SCSI, USB, FireWire, or eSATA, or via longer-distance technologies like Ethernet, iSCSI, or Fibre Channel. Some disk-based backup systems, via Virtual Tape Libraries or otherwise, support data deduplication, which can reduce the amount of disk storage capacity consumed by daily and weekly backup data.[29] [30] [31]

Optical storage

See also: Optical media preservation. Optical storage uses lasers to store and retrieve data. Recordable CDs, DVDs, and Blu-ray Discs are commonly used with personal computers and are generally cheap. The capacities and speeds of these discs have typically been lower than hard disks or tapes. Advances in optical media may shrink that gap in the future.[32] [33]

Potential future data losses caused by gradual media degradation can be predicted by measuring the rate of correctable minor data errors, of which consecutively too many increase the risk of uncorrectable sectors. Support for error scanning varies among optical drive vendors.[34]

Many optical disc formats are WORM type, which makes them useful for archival purposes since the data cannot be changed. Moreover, optical discs are not vulnerable to head crashes, magnetism, imminent water ingress or power surges; and, a fault of the drive typically just halts the spinning.

Optical media is modular; the storage controller is not tied to media itself like with hard drives or flash storage (→flash memory controller), allowing it to be removed and accessed through a different drive. However, recordable media may degrade earlier under long-term exposure to light.[35]

Some optical storage systems allow for cataloged data backups without human contact with the discs, allowing for longer data integrity. A French study in 2008 indicated that the lifespan of typically-sold CD-Rs was 2–10 years,[36] but one manufacturer later estimated the longevity of its CD-Rs with a gold-sputtered layer to be as high as 100 years.[37] Sony's proprietary Optical Disc Archive can in 2016 reach a read rate of 250 MB/s.[38]

Solid-state drive

Solid-state drives (SSDs) use integrated circuit assemblies to store data. Flash memory, thumb drives, USB flash drives, CompactFlash, SmartMedia, Memory Sticks, and Secure Digital card devices are relatively expensive for their low capacity, but convenient for backing up relatively low data volumes. A solid-state drive does not contain any movable parts, making it less susceptible to physical damage, and can have huge throughput of around 500 Mbit/s up to 6 Gbit/s. Available SSDs have become more capacious and cheaper.[39] [26] Flash memory backups are stable for fewer years than hard disk backups.

Remote backup service

Remote backup services or cloud backups involve service providers storing data offsite. This has been used to protect against events such as fires, floods, or earthquakes which could destroy locally stored backups.[40] Cloud-based backup (through services like or similar to Google Drive, and Microsoft OneDrive) provides a layer of data protection. However, the users must trust the provider to maintain the privacy and integrity of their data, with confidentiality enhanced by the use of encryption. Because speed and availability are limited by a user's online connection, users with large amounts of data may need to use cloud seeding and large-scale recovery.

Management

Various methods can be used to manage backup media, striking a balance between accessibility, security and cost. These media management methods are not mutually exclusive and are frequently combined to meet the user's needs. Using on-line disks for staging data before it is sent to a near-line tape library is a common example.[41] [42]

Online

Online backup storage is typically the most accessible type of data storage, and can begin a restore in milliseconds. An internal hard disk or a disk array (maybe connected to SAN) is an example of an online backup. This type of storage is convenient and speedy, but is vulnerable to being deleted or overwritten, either by accident, by malevolent action, or in the wake of a data-deleting virus payload.

Near-line

Nearline storage is typically less accessible and less expensive than online storage, but still useful for backup data storage. A mechanical device is usually used to move media units from storage into a drive where the data can be read or written. Generally it has safety properties similar to on-line storage. An example is a tape library with restore times ranging from seconds to a few minutes.

Off-line

Off-line storage requires some direct action to provide access to the storage media: for example, inserting a tape into a tape drive or plugging in a cable. Because the data is not accessible via any computer except during limited periods in which they are written or read back, they are largely immune to on-line backup failure modes. Access time varies depending on whether the media are on-site or off-site.

Off-site data protection

Backup media may be sent to an off-site vault to protect against a disaster or other site-specific problem. The vault can be as simple as a system administrator's home office or as sophisticated as a disaster-hardened, temperature-controlled, high-security bunker with facilities for backup media storage. A data replica can be off-site but also on-line (e.g., an off-site RAID mirror).

Backup site

A backup site or disaster recovery center is used to store data that can enable computer systems and networks to be restored and properly configured in the event of a disaster. Some organisations have their own data recovery centres, while others contract this out to a third-party. Due to high costs, backing up is rarely considered the preferred method of moving data to a DR site. A more typical way would be remote disk mirroring, which keeps the DR data as up to date as possible.

Selection and extraction of data

A backup operation starts with selecting and extracting coherent units of data. Most data on modern computer systems is stored in discrete units, known as files. These files are organized into filesystems. Deciding what to back up at any given time involves tradeoffs. By backing up too much redundant data, the information repository will fill up too quickly. Backing up an insufficient amount of data can eventually lead to the loss of critical information.[43]

Files

Making copies of files is the simplest and most common way to perform a backup. A means to perform this basic function is included in all backup software and all operating systems.

Filesystems

A versioning filesystem tracks all changes to a file. The NILFS versioning filesystem for Linux is an example.[46]

Live data

Files that are actively being updated present a challenge to back up. One way to back up live data is to temporarily quiesce them (e.g., close all files), take a "snapshot", and then resume live operations. At this point the snapshot can be backed up through normal methods.[47] A snapshot is an instantaneous function of some filesystems that presents a copy of the filesystem as if it were frozen at a specific point in time, often by a copy-on-write mechanism. Snapshotting a file while it is being changed results in a corrupted file that is unusable. This is also the case across interrelated files, as may be found in a conventional database or in applications such as Microsoft Exchange Server. The term fuzzy backup can be used to describe a backup of live data that looks like it ran correctly, but does not represent the state of the data at a single point in time.[48]

Backup options for data files that cannot be or are not quiesced include:[49]

Metadata

Not all information stored on the computer is stored in files. Accurately recovering a complete system from scratch requires keeping track of this non-file data too.[54]

The boot sector can sometimes be recreated more easily than saving it. It usually isn't a normal file and the system won't boot without it.

Manipulation of data and dataset optimization

It is frequently useful or required to manipulate the data being backed up to optimize the backup process. These manipulations can improve backup speed, restore speed, data security, media usage and/or reduced bandwidth requirements.

Automated data grooming

Out-of-date data can be automatically deleted, but for personal backup applications—as opposed to enterprise client-server backup applications where automated data "grooming" can be customized—the deletion[55] [56] [57] can at most[58] be globally delayed or be disabled.[59]

Compression

Various schemes can be employed to shrink the size of the source data to be stored so that it uses less storage space. Compression is frequently a built-in feature of tape drive hardware.[60]

Deduplication

Redundancy due to backing up similarly configured workstations can be reduced, thus storing just one copy. This technique can be applied at the file or raw block level. This potentially large reduction is called deduplication. It can occur on a server before any data moves to backup media, sometimes referred to as source/client side deduplication. This approach also reduces bandwidth required to send backup data to its target media. The process can also occur at the target storage device, sometimes referred to as inline or back-end deduplication.

Duplication

Sometimes backups are duplicated to a second set of storage media. This can be done to rearrange the archive files to optimize restore speed, or to have a second copy at a different location or on a different storage medium—as in the disk-to-disk-to-tape capability of Enterprise client-server backup.

Encryption

High-capacity removable storage media such as backup tapes present a data security risk if they are lost or stolen.[61] Encrypting the data on these media can mitigate this problem, however encryption is a CPU intensive process that can slow down backup speeds, and the security of the encrypted backups is only as effective as the security of the key management policy.

Multiplexing

When there are many more computers to be backed up than there are destination storage devices, the ability to use a single storage device with several simultaneous backups can be useful.[62] However cramming the scheduled backup window via "multiplexed backup" is only used for tape destinations.

Refactoring

The process of rearranging the sets of backups in an archive file is known as refactoring. For example, if a backup system uses a single tape each day to store the incremental backups for all the protected computers, restoring one of the computers could require many tapes. Refactoring could be used to consolidate all the backups for a single computer onto a single tape, creating a "synthetic full backup". This is especially useful for backup systems that do incrementals forever style backups.

Staging

Sometimes backups are copied to a staging disk before being copied to tape. This process is sometimes referred to as D2D2T, an acronym for Disk-to-disk-to-tape. It can be useful if there is a problem matching the speed of the final destination device with the source device, as is frequently faced in network-based backup systems. It can also serve as a centralized location for applying other data manipulation techniques.

Objectives

In addition to preserving access to data for its owners, data must be restricted from unauthorized access. Backups must be performed in a manner that does not compromise the original owner's undertaking. This can be achieved with data encryption and proper media handling policies.[65]

Enterprise client-server backup applications need a user interface that allows administrators to monitor the backup process, and proves compliance to regulatory bodies outside the organization; for example, an insurance company in the USA might be required under HIPAA to demonstrate that its client data meet records retention requirements.[67]

To avoid or recover from minor disasters, such as inadvertently deleting or overwriting the "good" versions of one or more files, the computer user—rather than an administrator—may initiate backups and restores (from not necessarily the most-recent backup) of files or folders.

See also

About backup

Related topics

Notes and References

  1. Web site: back•up . The American Heritage Dictionary of the English Language . Houghton Mifflin Harcourt . 9 May 2018 . 2018.
  2. Book: Pro Data Backup and Recovery . Chapter 1: Introduction to Backup and Recovery . S. Nelson . Apress . 1–16 . 2011 . 978-1-4302-2663-5 . 8 May 2018.
  3. Book: https://books.google.com/books?id=eLviiTag5A0C&pg=PA1 . The Backup Book: Disaster Recovery from Desktop to Data Center . Chapter 1: What's a Disaster Without a Recovery? . Cougias, D.J. . Heiberger, E.L. . Koop, K. . Network Frontiers . 1–14 . 2003 . 0-9729039-0-9.
  4. In contrast to everyday use of the term "archive", the data stored in an "archive file" is not necessarily old or of historical interest.
  5. Book: Joe Kissell . Take Control of Mac OS X Backups . 2007 . TidBITS Electronic Publishing . Ithaca, NY . 978-0-9759503-0-2 . Version 2.0 . 17 May 2019 . Kissell . 18–20 ("The Archive", meaning information repository, including versioning), 24 (client-server), 82–83 (archive file), 112–114 (Off-site storage backup rotation scheme), 126–141 (old Retrospect terminology and GUI—still used in Windows variant), 165 (client-server), 128 (subvolume—later renamed Favorite Folder in Macintosh variant) . 1 December 2020 . https://web.archive.org/web/20201201201812/http://people.fas.harvard.edu/~techtool/pages/Take_Control_of_Mac_OS_X_Backups_(2.0).pdf . dead .
  6. Ensuring the complete destruction of the primary site will not result in the loss of the recovery site by locating them physically far away.
    Web site: .ORG Sponsorship Proposal - Technical Plan - Physical Security . ICANN.
  7. News: . A Beginner's Guide to Backing Up Photos . Terry Sullivan . 11 January 2018 . a hard drive ... an established company ... declared bankruptcy ... where many ... had ....
  8. Web site: McMahon . Mary . What Is an Information Repository? . wiseGEEK . Conjecture Corporation . 8 May 2019 . 1 April 2019 . In the sense of an approach to data management, an information repository is a secondary storage space for data..
  9. Web site: Five key questions to ask about your backup solution . sysgen.ca . 23 September 2015 . https://web.archive.org/web/20160304042343/http://sysgen.ca/five-key-backup-questions/ . 4 March 2016 . live . dmy-all. Does your company have a low tolerance to longer "data access outages" and/or would you like to minimize the time your company may be without its data?. 23 March 2014 .
  10. Web site: Incremental Backup . Tech-FAQ . Independent Media . 10 March 2006 . https://web.archive.org/web/20160621090117/http://www.tech-faq.com/incremental-backup.shtml . 21 June 2016 . 13 June 2005.
  11. Web site: Pond . James . How Time Machine Works its Magic . Apple OSX and Time Machine Tips . baligu.com . 19 May 2019 . 31 August 2013 . File System Event Store, Hard Links . 21 June 2019 . https://web.archive.org/web/20190621092705/https://www.baligu.com/pondini/TM/Works.html . dead .
  12. Web site: Behzad Behtash . Why Continuous Data Protection's Getting More Practical . Disaster recovery/business continuity . InformationWeek . 6 May 2010 . 12 November 2011 . A true CDP approach should capture all data writes, thus continuously backing up data and eliminating backup windows.... CDP is the gold standard—the most comprehensive and advanced data protection. But "near CDP" technologies can deliver enough protection for many companies with less complexity and cost. For example, snapshots can provide a reasonable near-CDP-level of protection for file shares, letting users directly access data on the file share at regular intervals--say, every half-hour or 15 minutes. That's certainly a higher level of protection than tape-based or disk-based nightly backups and may be all you need..
  13. Web site: Continuous data protection (CDP) explained: True CDP vs near-CDP . ComputerWeekly.com . TechTarget . 22 June 2019 . July 2010 . ... copies data from a source to a target. True CDP does this every time a change is made, while so-called near-CDP does this at pre-set time intervals. Near-CDP is effectively the same as snapshotting....True CDP systems record every write and copy them to the target where all changes are stored in a log. [new paragraph] By contrast, near-CDP/snapshot systems copy files in a straightforward manner but require applications to be quiesced and made ready for backup, either via the application's backup mode or using, for example, Microsoft's Volume Shadow Copy Services (VSS)..
  14. Web site: Pond . James . How Time Machine Works its Magic . Apple OSX and Time Machine Tips . Baligu.com (as mirrored after James Pond died in 2013) . 10 July 2019 . 31 August 2013 . The File System Event Store is a hidden log that OSX keeps on each HFS+ formatted disk/partition of changes made to the data on it. It doesn’t list every file that’s changed, but each directory (folder) that’s had anything changed inside it..
  15. Book: Enterprise Systems Backup and Recovery: A Corporate Insurance Policy . de Guise, P. . CRC Press . 285–287 . 2009 . 978-1-4200-7639-4.
  16. Web site: Wu . Victor . EMC RecoverPoint for Virtual Machine Overview . Victor Virtual . WuChiKin . 22 June 2019 . 4 March 2017 . The splitter splits out the Write IOs to the VMDK/RDM of a VM and sends a copy to the production VMDK and also to the RecoverPoint for VMs cluster..
  17. Web site: Zerto or Veeam? . RES-Q Services . 7 July 2019 . March 2017 . Zerto doesn’t use snapshot technology like Veeam. Instead, Zerto deploys small virtual machines on its physical hosts. These Zerto VMs capture the data as it is written to the host and then send a copy of that data to the replication site.....However, Veeam has the advantage of being able to more efficiently capture and store data for long-term retention needs. There is also a significant pricing difference, with Veeam being cheaper than Zerto..
  18. Web site: Agent Related . CloudEndure.com . 3 July 2019 . What does the CloudEndure Agent do? . 2019 . The CloudEndure Agent performs an initial block-level read of the content of any volume attached to the server and replicates it to the Replication Server. The Agent then acts as an OS-level read filter to capture writes and synchronizes any block level modifications to the CloudEndure Replication Server, ensuring near-zero RPO..
  19. Web site: 9 December 2004 . 26 May 2019 . Disk to Disk Backup versus Tape – War or Truce? . https://web.archive.org/web/20050207082953/http://www.storagesearch.com/engenio-art2.html . dead . 7 February 2005 . Gardner . Steve . Peaceful coexistence . Engenio .
  20. Web site: Digital Data Storage Outlook 2017 . Spectra . Spectra Logic . 11 July 2018 . 7(Solid-State), 10(Magnetic Disk), 14(Tape), 17(Optical) . 2017.
  21. Web site: Tom Coughlin . Keeping Data for a Long Time . Forbes . 19 April 2018 . 29 June 2014 . para. Magnetic Tapes(popular formats, storage life), para. Hard Disk Drives(active archive), para. First consider flash memory in archiving(... may not have good media archive life).
  22. Web site: Jacobi . John L. . Hard-core data preservation: The best media and methods for archiving your data . PC World . 19 April 2018 . 29 February 2016 . sec. External Hard Drives(on the shelf, magnetic properties, mechanical stresses, vulnerable to shocks), Tape, Online storage.
  23. Web site: Ramp Load/Unload Technology in Hard Disk Drives . HGST . Western Digital . 29 June 2018 . 3(sec. Enhanced Shock Tolerance) . November 2007.
  24. Web site: Toshiba Portable Hard Drive (Canvio® 3.0) . Toshiba Data Dynamics Singapore . Toshiba Data Dynamics Pte Ltd . 16 June 2018 . 2018 . sec. Overview(Internal shock sensor and ramp loading technology).
  25. Web site: Iomega Drop Guard ™ Technology . Hard Drive Storage Solutions . Iomega Corp. . 12 July 2018 . 2(What is Drop Shock Technology?, What is Drop Guard Technology? (... features special internal cushioning .... 40% above the industry average)), 3(*NOTE) . 20 September 2010.
  26. Web site: John Burek . The Best Rugged Hard Drives and SSDs . . Ziff Davis . 4 August 2018 . What Exactly Makes a Drive Rugged?(When a drive is encased ... you're mostly at the mercy of the drive vendor to tell you the rated maximum drop distance for the drive) . 15 May 2018.
  27. Web site: Justin Krajeski . Kimber Streams . The Best Portable Hard Drive . . 4 August 2018 . https://web.archive.org/web/20170331161821/http://thewirecutter.com/reviews/best-portable-hard-drive/#dont-buy-a-rugged-portable-hard-drive . dead . 31 March 2017 . 20 March 2017.
  28. Web site: Best Long-Term Data Archive Solutions . Iron Mountain . Iron Mountain Inc. . 19 April 2018 . 2018 . sec. More Reliable(average mean time between failure ... rates, best practice for migrating data).
  29. Book: Kissell . Joe . Take Control of Backing Up Your Mac . 2011 . TidBITS Publishing Inc. . Ithaca NY . 978-1-61542-394-1 . 41(Deduplication) . 17 September 2019.
  30. Web site: Symantec Shows Backup Exec a Little Dedupe Love; Lays out Source Side Deduplication Roadmap – DCIG . DCIG . 7 July 2009 . 26 February 2016 . https://web.archive.org/web/20160304212819/http://www.dcig.com/2009/07/symantec-shows-backup-exec-a-l.html . 4 March 2016 . live . dmy-all.
  31. Web site: Veritas NetBackup™ Deduplication Guide . Veritas . Veritas Technologies LLC . 26 July 2018 . 2016.
  32. Optical storage: An emerging option in long-term digital preservation . Frontiers of Optoelectronics . S. Wan . Q. Cao . C. Xie . 7 . 4 . 486–492 . 2014 . 10.1007/s12200-014-0442-2. 60816607 .
  33. High-capacity optical long data memory based on enhanced Young's modulus in nanoplasmonic hybrid glass composites. Nature Communications. Q. Zhang . Z. Xia . Y.-B. Cheng . M. Gu. 9 . 1. 1183 . 2018 . 10.1038/s41467-018-03589-y. 29568055. 2018NatCo...9.1183Z. 5864957 .
  34. Web site: Bärwaldt . Erik . Full Control » Linux Magazine . Linux Magazine . 2014.
  35. Web site: 5. Conditions That Affect CDs and DVDs • CLIR . CLIR.
  36. Web site: Journal de 20 Heures . 3 March 2008 . approximately minute 30 of the TV news broadcast . Institut national de l'audiovisuel . Gérard Poirier . Foued Berahou . 3 March 2008.
  37. Web site: Archival Gold CD-R "300 Year Disc" Binder of 10 Discs with Scratch Armor Surface . 27 September 2013 . https://web.archive.org/web/20130927170900/http://delkin.com/i-5937134-archival-gold-cd-r-300-year-disc-binder-of-10-discs-with-scratch-armor-surface.html . Delkin Devices . Delkin Devices Inc..
  38. Web site: Optical Disc Archive Generation 2 . Optical Disc Archive . Sony . 15 August 2019 . 12(World’s First 8-Channel Optical Drive Unit) . April 2016.
  39. Solid-State Drives (SSDs) . Proceedings of the IEEE . R. Micheloni . P. Olivo . 105 . 9 . 1586–88 . 2017 . 10.1109/JPROC.2017.2727228 .
  40. Web site: Remote Backup . EMC Glossary . Dell, Inc . 8 May 2018 . Effective remote backup requires that production data be regularly backed up to a location far enough away from the primary location so that both locations would not be affected by the same disruptive event..
  41. Book: Software Deployment, Updating, and Patching . Stackpole, B. . Hanrion, P. . CRC Press . 164–165 . 2007 . 978-1-4200-1329-0 . 8 May 2018.
  42. Book: Information Storage and Management: Storing, Managing, and Protecting Digital Information in Classic, Virtualized, and Cloud Environments . Gnanasundaram, S. . Shrivastava, A. . John Wiley and Sons . 255 . 2012 . 978-1-118-23696-3 . 8 May 2018.
  43. Web site: What to backup – a critical look at your data . Lee . Irontree Blog . Irontree Internet Services CC . 25 January 2017 . 8 May 2018.
  44. Book: Backup & Recovery: Inexpensive Backup Solutions for Open Systems . Preston, W.C. . O'Reilly Media, Inc . 111–114 . 2007 . 978-0-596-55504-7 . 8 May 2018.
  45. Book: Unix Backup & Recovery . registration . Preston, W.C. . O'Reilly Media, Inc . 73–91 . 1999 . 978-1-56592-642-4 . 8 May 2018.
  46. Web site: NILFS Home . NILFS Continuous Snapshotting System . NILFS Community . 22 August 2019 . 2019.
  47. Book: https://books.google.com/books?id=eLviiTag5A0C&pg=PA360. The Backup Book: Disaster Recovery from Desktop to Data Center . Chapter 11: Open file backup for databases . Cougias, D.J. . Heiberger, E.L. . Koop, K. . Network Frontiers . 356–360 . 2003 . 0-9729039-0-9.
  48. Book: Mission-critical Network Planning . Liotine, M. . Artech House . 244 . 2003 . 978-1-58053-559-5 . 8 May 2018.
  49. Book: Enterprise Systems Backup and Recovery: A Corporate Insurance Policy . de Guise, P. . CRC Press . 50–54 . 2009 . 978-1-4200-7639-4.
  50. Web site: Open File Backup Software for Windows . Handy Backup . Novosoft LLC . 29 November 2018 . 8 November 2018.
  51. Web site: Reitshamer . Stefan . Troubleshooting backing up open/locked files on Windows . Arq Blog . Haystack Software . 29 November 2018 . 5 July 2017 . Stefan Reitshamer is the principal developer of Arq.
  52. Web site: Boss . Nina . Oracle Tips Session #3: Oracle Backups . https://web.archive.org/web/20070302110933/http://www.wisc.edu/drmt/oratips/sess003.html#Hotbackup . dead . www.wisc.edu . University of Wisconsin . 1 December 2018 . 2 March 2007 . 10 December 1997.
  53. Web site: What is ARCHIVE-LOG and NO-ARCHIVE-LOG mode in Oracle and the advantages & disadvantages of these modes? . Arcserve Backup . Arcserve . 29 November 2018 . 27 September 2018.
  54. Web site: Preparation of Bootable Media and Images . Grešovnik . Igor . April 2016 . https://web.archive.org/web/20160425113119/http://www2.arnes.si/~ljc3m2/igor/blogs/technical/bootable_media_creation.html . 25 April 2016 . 21 April 2016.
  55. Some backup applications—notably rsync and CrashPlan—term removing backup data "pruning" instead of "grooming".
  56. Web site: rsync(1) - Linux man page. linux.die.net. Andrew . Tridgell . Paul . Mackerras. Wayne . Davison.
  57. Web site: Archive maintenance. 2023. Code42 Support.
  58. Web site: Pond . James . 12. Should I delete old backups? If so, How? . Time Machine . baligu.com . 21 June 2019 . Green box, Gray box . 2 June 2012.
  59. Web site: Kissell . Joe . The Best Online Cloud Backup Service . wirecutter . The New York Times. 21 June 2019 . Next, there’s file retention. . 12 March 2019.
  60. Book: Securing SQL Server: Protecting Your Database from Attackers . D. Cherry . Syngress . 306–308 . 2015 . 978-0-12-801375-5 . 8 May 2018.
  61. http://www.securityfocus.com/news/11048 Backups tapes a backdoor for identity thieves
  62. Book: Backup & Recovery: Inexpensive Backup Solutions for Open Systems . Preston, W.C. . O'Reilly Media, Inc . 219–220 . 2007 . 978-0-596-55504-7 . 8 May 2018.
  63. Web site: Recovery Point Objective (Definition) . ARL Risky Thinking . Albion Research Ltd. . 4 August 2019 . 2007.
  64. Web site: Recovery Time Objective (Definition) . ARL Risky Thinking . Albion Research Ltd. . 4 August 2019 . 2007.
  65. Book: https://books.google.com/books?id=_DqO6kizEDUC&pg=PA17 . Implementing Backup and Recovery: The Readiness Guide for the Enterprise . Chapter 2: Business Requirements of Backup Systems . Little, D.B. . John Wiley and Sons . 17–30 . 2003 . 978-0-471-48081-5 . 8 May 2018.
  66. Web site: How do the "verify" and "write checksums to media" processes work and why are they necessary? . Veritas Support . Veritas.com . 16 September 2019 . 15 October 2015 . Write checksums to media.
  67. http://www.hipaadvisory.com/regs/recordretention.htm HIPAA Advisory