Editing Backup (section)

{{Short description|Stored data in computer systems}}
{{about|duplicate data in computer systems for data recovery|other uses|Backup (disambiguation)}}
{{Use dmy dates|date=October 2019}}

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 "[[wikt:back up|back up]]", whereas the noun and adjective form is "[[wikt:backup|backup]]".<ref name="AHDictionaryBackup">{{cite web |title=back•up |url=https://www.ahdictionary.com/word/search.html?q=backup |website=The American Heritage Dictionary of the English Language |publisher=Houghton Mifflin Harcourt |access-date=9 May 2018 |year=2018}}</ref> Backups can be used to [[data recovery|recover data]] after its loss from [[File deletion|data deletion]] or [[Data corruption|corruption]], or to recover data from an earlier time.{{Nbsp|2=hair}}<ref name="NelsonPro11">{{cite book
   |url=https://books.google.com/books?id=r4uEEsq3CJYC
   |title=Pro Data Backup and Recovery
   |chapter=Chapter 1: Introduction to Backup and Recovery
   |author=S. Nelson |publisher=Apress |pages=1–16 |year=2011
   |isbn=978-1-4302-2663-5 |access-date=8 May 2018}}</ref> Backups provide a simple form of [[IT 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]].<ref name="CougiasTheBackup03Chapter01">{{cite book |chapter-url=https://books.google.com/books?id=eLviiTag5A0C&pg=PA1 |title=The Backup Book: Disaster Recovery from Desktop to Data Center |chapter=Chapter 1: What's a Disaster Without a Recovery? |author=Cougias, D.J. |author2=Heiberger, E.L. |author3=Koop, K. |publisher=Network Frontiers |pages=1–14 |year=2003 |isbn=0-9729039-0-9}}</ref>

A backup system contains at least one copy of all data considered worth saving. The [[computer data storage|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 device]]s used for copying backups of data that is already in secondary storage onto [[archive file]]s.<ref group = note name=ArchiveFileMayNotContainOld/HistoricalMaterial>In contrast to everyday use of the term "archive", the data stored in an "archive file" is not necessarily old or of historical interest.</ref><ref name="KissellTakeControlMacOSX">{{cite book
   |author=Joe Kissell
   |title=Take Control of Mac OS X Backups
   |date=2007
   |publisher=TidBITS Electronic Publishing
   |location=Ithaca, NY
   |isbn=978-0-9759503-0-2
   |edition=Version 2.0
   |url=http://people.fas.harvard.edu/~techtool/pages/Take_Control_of_Mac_OS_X_Backups_(2.0).pdf
   |access-date=17 May 2019
   |ref=Kissell
   |pages=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)
   |archive-date=1 December 2020
   |archive-url=https://web.archive.org/web/20201201201812/http://people.fas.harvard.edu/~techtool/pages/Take_Control_of_Mac_OS_X_Backups_(2.0).pdf
   |url-status=dead
   }}</ref> There are also different ways these devices can be arranged to provide geographic dispersion,<ref>Ensuring the complete destruction of the primary site will not result in the loss of the recovery site by locating them physically far away. <br/>
{{cite web |url=https://archive.icann.org/en/tlds/org/applications/isoc/section3.html#c17.9-2 |title=.ORG Sponsorship Proposal - Technical Plan - Physical Security |publisher=[[ICANN]]}}</ref> [[data security]], and [[data portability|portability]].

Data is selected, extracted, and manipulated for storage. The process can include methods for [[Data consistency#Point-in-time consistency|dealing with live data]], including open files, as well as compression, encryption, and [[Data deduplication|de-duplication]]. Additional techniques apply to [[enterprise client-server backup]]. Backup schemes may include [[Dry run (testing)|dry runs]] that validate the reliability of the data being backed up. There are limitations<ref name=OutaBiz>{{cite news  |newspaper=[[The New York Times]]
   |url=https://www.nytimes.com/2018/01/11/smarter-living/backing-up-your-photos.html
   |title=A Beginner's Guide to Backing Up Photos
   |author=Terry Sullivan  |date=11 January 2018
   |quote=a hard drive ... an established company ... declared bankruptcy ... where many ... had ...}}</ref> and human factors involved in any backup scheme.