Editing Backup (section)

==Storage==
A backup strategy requires an information repository, "a secondary storage space for data"<ref name="wiseGEEKInformationRepository">{{cite web |last1=McMahon |first1=Mary |title=What Is an Information Repository? |url=https://www.wisegeek.com/what-is-an-information-repository.htm |website=wiseGEEK |publisher=Conjecture Corporation |access-date=8 May 2019 |date=1 April 2019 |quote=In the sense of an approach to data management, an information repository is a secondary storage space for data.}}</ref> 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]].

===3-2-1 Backup Rule===
The backup data needs to be stored, requiring a [[backup rotation scheme]],<ref name="KissellTakeControlMacOSX" /> 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 crash]]es 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.

Because there is no perfect storage, many backup experts recommend maintaining a second copy on a local physical device, even if the data is also backed up offsite.<ref>
Jeph Preece.
[https://web.archive.org/web/20160816162547/http://www.toptenreviews.com/services/internet/best-online-data-backup-services/ "Online Data Backup Reviews: Why Use an Online Data Backup Service?"].
Top Ten Reviews.
2016.
</ref><ref>
Kyle Chin.
[https://www.upguard.com/blog/how-to-back-up-your-data "How to Back Up Your Data: 6 Effective Strategies to Prevent Data Loss"].
2024.
</ref><ref>
[https://www.kingston.com/en/blog/personal-storage/how-to-backup-drives-windows-mac "How do you backup your computer? Windows and Mac drive backup"].
2023.
</ref><ref>
Scott Gilbertson.
[https://www.wired.com/story/how-to-back-up-your-digital-life/ "How to Back Up Your Digital Life"].
2024.
</ref>

===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 image]]s, this method is frequently used by computer technicians to record known good configurations. However, imaging<ref>{{Cite web |title=Five key questions to ask about your backup solution |url=http://sysgen.ca/five-key-backup-questions/ |website=sysgen.ca |access-date=23 September 2015 |archive-url=https://web.archive.org/web/20160304042343/http://sysgen.ca/five-key-backup-questions/ |archive-date=4 March 2016 |url-status=live |df=dmy-all|at=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?|date=23 March 2014 }}</ref> 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.<ref name="Tech-FAQIncrementalBackup">{{cite web |title=Incremental Backup |url=http://www.tech-faq.com/incremental-backup.shtml |website=Tech-FAQ |publisher=Independent Media |access-date=10 March 2006 |archive-url=https://web.archive.org/web/20160621090117/http://www.tech-faq.com/incremental-backup.shtml |archive-date=21 June 2016 |date=13 June 2005}}</ref>
Some backup systems<ref name="PondHowTimeMachineWorks">{{cite web | last1=Pond | first1=James | url=http://baligu.com/pondini/TM/Works.html | title=How Time Machine Works its Magic | website=Apple OSX and Time Machine Tips | publisher=baligu.com | access-date=19 May 2019 | date=31 August 2013 | at=File System Event Store, Hard Links | archive-date=21 June 2019 | archive-url=https://web.archive.org/web/20190621092705/https://www.baligu.com/pondini/TM/Works.html | url-status=dead }}</ref> can create a {{visible anchor|synthetic full backup}} 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{{anchor|Continuous_data_protection}}====
[[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.<ref name=InformationWeekWhyCDPGettingMorePractical>{{cite web
   |author=Behzad Behtash
   |url=https://www.informationweek.com/why-continuous-data-protections-getting-more-practical/d/d-id/1088883
   |title=Why Continuous Data Protection's Getting More Practical
   |work=Disaster recovery/business continuity
   |publisher=InformationWeek |date=6 May 2010 |access-date=12 November 2011 |quote=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.}}</ref> Near-CDP backup applications—often [[List of backup software#Proprietary|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.<ref name=InformationWeekWhyCDPGettingMorePractical /> Near-CDP backup applications use [[Journaling file system|journaling]] and are typically based on periodic "snapshots",<ref name="ComputerWeeklyCDPExplained">{{cite web |title=Continuous data protection (CDP) explained: True CDP vs near-CDP |url=https://www.computerweekly.com/Continuous-data-protection-CDP-explained-True-CDP-vs-near-CDP |website=ComputerWeekly.com |publisher=TechTarget |access-date=22 June 2019 |date=July 2010 |quote=... 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).}}</ref> [[file system permissions|read-only]] copies of the data frozen at a particular [[point in time]].

Near-CDP (except for [[Apple Time Machine]])<ref name="PondiniHowTMWorksItsMagic">{{cite web |last1=Pond |first1=James |title=How Time Machine Works its Magic |url=https://www.baligu.com/pondini/TM/Works.html |website=Apple OSX and Time Machine Tips |publisher=Baligu.com (as mirrored after James Pond died in 2013) |access-date=10 July 2019 |date=31 August 2013 |quote=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.}}</ref> [[Intent log|intent-logs]] every change on the host system,<ref name="deGuiseEnterprise09#A.3.3">{{cite book |url=https://books.google.com/books?id=2OtqvySBTu4C&pg=PA287|title=Enterprise Systems Backup and Recovery: A Corporate Insurance Policy |author=de Guise, P. |publisher=CRC Press |pages=285–287 |year=2009 |isbn=978-1-4200-7639-4}}</ref> 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<ref name="VictorWuEMCRecoverPointVM">{{cite web |last1=Wu |first1=Victor |title=EMC RecoverPoint for Virtual Machine Overview |url=https://wuchikin.wordpress.com/2017/03/04/emc-recoverpoint-for-virtual-machine-overview/ |website=Victor Virtual |publisher=WuChiKin |access-date=22 June 2019 |date=4 March 2017 |quote=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.}}</ref><ref name="RES-QServicesZertoOrVeeam">{{cite web |title=Zerto or Veeam? |url=https://resqdr.com/zerto-or-veeam/ |website=RES-Q Services |access-date=7 July 2019 |date=March 2017 |quote=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.}}</ref> or equivalent<ref name="CloudEndureAgentRelated">{{cite web |title=Agent Related |url=https://docs.cloudendure.com/Content/FAQ/FAQ/Agent_Related.htm |website=CloudEndure.com |access-date=3 July 2019 |at=What does the CloudEndure Agent do? |date=2019 |quote=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.}}</ref> 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 file|".bak" extension]] to the [[file name]].

====Reverse incremental====
A [[Incremental backup#Reverse incremental|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===
[[File:DVD, USB flash drive and external hard drive.jpg|thumb|right|From left to right, a [[DVD]] disc in plastic cover, a USB flash drive and an [[external hard drive]]]]
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 data storage|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.<ref name=EngenioDiskToDiskVsTape>{{cite web  |date=9 December 2004  |access-date=26 May 2019
   |url=http://www.storagesearch.com/engenio-art2.html  |archive-url=https://web.archive.org/web/20050207082953/http://www.storagesearch.com/engenio-art2.html  |url-status=dead  |archive-date=7 February 2005  |title=Disk to Disk Backup versus Tape – War or Truce? |last1=Gardner |first1=Steve |at=Peaceful coexistence |publisher=Engenio
 }}</ref> 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 drive]]s are typically dozens of times as expensive as [[hard disk drive]]s and [[optical drive]]s.

Many tape formats have been proprietary or specific to certain markets like mainframes or a particular brand of personal computer. By 2014 [[Linear Tape-Open#Market performance|LTO]] had become the primary tape technology.<ref name="SpectraLogicDigitalDataStorageOutlook2017">{{cite web |title=Digital Data Storage Outlook 2017 |url=https://spectralogic.com/wp-content/uploads/white-paper-digital-data-storage-outlook-2017-v3.pdf |website=Spectra |publisher=Spectra Logic |access-date=11 July 2018 |page=7(Solid-State), 10(Magnetic Disk), 14(Tape), 17(Optical) |year=2017}}</ref> The other remaining viable "super" format is the [[IBM 3592]] (also referred to as the TS11xx series). The [[StorageTek tape formats#T10000|Oracle StorageTek T10000]] was discontinued in 2016.<ref name="ForbesKeepingDataLongTime">{{cite web |author=Tom Coughlin  |title=Keeping Data for a Long Time |url=https://www.forbes.com/sites/tomcoughlin/2014/06/29/keeping-data-for-a-long-time/ |website=Forbes |access-date=19 April 2018 |date=29 June 2014 |at=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)}}</ref>

====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.<ref name="SpectraLogicDigitalDataStorageOutlook2017" /> However, hard disk backups are [[Hard disk drive#Magnetic recording|close-tolerance mechanical devices]] and may be more easily damaged than tapes, especially while being transported.<ref name="PCWorldHardCoreDataPreservation">{{cite web |last1=Jacobi |first1=John L. |title=Hard-core data preservation: The best media and methods for archiving your data |url=https://www.pcworld.com/article/2984597/storage/hard-core-data-preservation-the-best-media-and-methods-for-archiving-your-data.html |website=PC World |access-date=19 April 2018 |date=29 February 2016 |at=sec. External Hard Drives(on the shelf, magnetic properties, mechanical stresses, vulnerable to shocks), Tape, Online storage}}</ref> In the mid-2000s, several drive manufacturers began to produce portable drives employing [[Hard disk drive failure#Unloading|ramp loading and accelerometer]] technology (sometimes termed a "shock sensor"),<ref name="HGSTRampLoadUnload">{{cite web |title=Ramp Load/Unload Technology in Hard Disk Drives |url=https://www.hgst.com/sites/default/files/resources/LoadUnload_white_paper_FINAL.pdf |website=HGST |publisher=Western Digital |access-date=29 June 2018 |page=3(sec. Enhanced Shock Tolerance) |date=November 2007}}</ref><ref name="ToshibaCanvio3.0PortableHDD">{{cite web |title=Toshiba Portable Hard Drive (Canvio® 3.0) |url=https://www.toshibadata.com.sg/Product-Canvio-Portable-Hard-Drive.aspx |website=Toshiba Data Dynamics Singapore |publisher=Toshiba Data Dynamics Pte Ltd |access-date=16 June 2018 |year=2018 |at=sec. Overview(Internal shock sensor and ramp loading technology)}}</ref> 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.<ref name="IomegaDropShock">{{cite web |title=Iomega Drop Guard ™ Technology |url=https://www.doc-developpement-durable.org/file/Projets-informatiques/Drop%20Guard-disque-dur-tres-solide.pdf |website=Hard Drive Storage Solutions |publisher=Iomega Corp. |access-date=12 July 2018 |pages=2(What is Drop Shock Technology?, What is Drop Guard Technology? (... features special internal cushioning .... 40% above the industry average)), 3(*NOTE) |date=20 September 2010}}</ref> Some manufacturers also offer 'ruggedized' portable hard drives, which include a shock-absorbing case around the hard disk, and [[MIL-STD-810#Applicability to "ruggedized" consumer products|claim]] a range of higher drop specifications.<ref name="IomegaDropShock" /><ref name=PCMagBest>
{{cite web |author=John Burek
   |title=The Best Rugged Hard Drives and SSDs
   |url=https://www.pcmag.com/roundup/361072/the-best-rugged-hard-drives-and-ssds
   |website=[[PC Magazine]] |publisher=Ziff Davis |access-date=4 August 2018
   |at=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) |date=15 May 2018}}</ref><ref name="WirecutterBestPortableHardDrive2017Don'tBuy">{{cite web
   |author=Justin Krajeski  |author2=Kimber Streams 
   |title=The Best Portable Hard Drive
   |url=http://thewirecutter.com/reviews/best-portable-hard-drive/#dont-buy-a-rugged-portable-hard-drive
   |work=[[The New York Times]] |access-date=4 August 2018
   |archive-url=https://web.archive.org/web/20170331161821/http://thewirecutter.com/reviews/best-portable-hard-drive/#dont-buy-a-rugged-portable-hard-drive  |url-status=dead  |archive-date=31 March 2017 |date=20 March 2017}}</ref> Over a period of years the stability of hard disk backups is shorter than that of tape backups.<ref name="ForbesKeepingDataLongTime" /><ref name="IronMountainBestLong-TermDataArchiveSolutions">{{cite web |title=Best Long-Term Data Archive Solutions |url=http://www.ironmountain.com/resources/general-articles/b/best-long-term-data-archive-solutions |website=Iron Mountain |publisher=Iron Mountain Inc. |access-date=19 April 2018 |year=2018 |at=sec. More Reliable(average mean time between failure ... rates, best practice for migrating data)}}</ref><ref name="PCWorldHardCoreDataPreservation" />

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 library|Virtual Tape Libraries]] or otherwise, support data deduplication, which can reduce the amount of disk storage capacity consumed by daily and weekly backup data.<ref name="KissellTakeControlBackingUp">{{cite book |last1=Kissell |first1=Joe |title=Take Control of Backing Up Your Mac |date=2011 |publisher=TidBITS Publishing Inc. |location=Ithaca NY |isbn=978-1-61542-394-1 |page=41(Deduplication) |url=https://books.google.com/books?id=ANe3k_7bnAcC&q=retrospect+deduplication&pg=PT41 |access-date=17 September 2019}}</ref><ref>{{Cite web |url=http://www.dcig.com/2009/07/symantec-shows-backup-exec-a-l.html |title=Symantec Shows Backup Exec a Little Dedupe Love; Lays out Source Side Deduplication Roadmap – DCIG |website=DCIG |date=7 July 2009 |access-date=26 February 2016 |archive-url=https://web.archive.org/web/20160304212819/http://www.dcig.com/2009/07/symantec-shows-backup-exec-a-l.html |archive-date=4 March 2016 |url-status=live |df=dmy-all}}</ref><ref name="NetBackupDeduplicationGuide">{{cite web |title=Veritas NetBackup™ Deduplication Guide |url=https://www.veritas.com/content/support/en_US/doc/ka6j00000000ADEAA2 |website=Veritas |publisher=Veritas Technologies LLC |access-date=26 July 2018 |year=2016}}</ref>

====Optical storage====
[[File:Water running on CD-RW - label side.jpg|thumb|Optical discs are not vulnerable to water, making them likely to survive a flood disaster.]]
{{See also|Optical media preservation}}
[[Optical storage]] uses lasers to store and retrieve data. Recordable [[CD]]s, DVDs, and [[Blu-ray Disc]]s 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.<ref name="WanOptical14">{{cite journal
   |title=Optical storage: An emerging option in long-term digital preservation
   |journal=Frontiers of Optoelectronics
   |author1=S. Wan |author2=Q. Cao |author3=C. Xie |volume=7 |issue=4 |pages=486–492 |year=2014
   |doi=10.1007/s12200-014-0442-2|s2cid=60816607
 }}</ref><ref>{{cite journal
|title=High-capacity optical long data memory based on enhanced Young's modulus in nanoplasmonic hybrid glass composites
|journal=Nature Communications
|author1=Q. Zhang |author2=Z. Xia |author3=Y.-B. Cheng |author4=M. Gu
|volume=9 |issue=1
|pages=1183 |year=2018 |doi=10.1038/s41467-018-03589-y|pmid=29568055
|bibcode=2018NatCo...9.1183Z
|pmc=5864957 }}</ref>

Potential future data losses caused by gradual [[disc rot|media degradation]] can be [[Predictive failure analysis|predicted]] by  [[optical disc#Surface error scanning|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.<ref>{{cite web |last1=Bärwaldt |first1=Erik |title=Full Control » Linux Magazine |url=https://www.linux-magazine.com/Issues/2014/169/QPxTool |website=Linux Magazine |date=2014}}</ref>

Many optical disc formats are [[Write Once Read Many|WORM]] type, which makes them useful for archival purposes since the data cannot be changed in any way, including by user error and by malware such as [[ransomware]]. Moreover, optical discs are [[fault tolerance|not vulnerable]] to [[head crash]]es, magnetism, imminent water ingress or [[Voltage spike|power surge]]s; and, a fault of the drive typically just halts the spinning.

Optical media is [[modularity|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.<ref>{{cite web |title=5. Conditions That Affect CDs and DVDs • CLIR |url=https://www.clir.org/pubs/reports/pub121/sec5/ |website=CLIR}}</ref>

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-R#Lifespan|CD-Rs]] was 2–10 years,<ref name=INA_CD-R_Study>{{cite web
   |url=http://www.ina.fr/video/3571726001/20-heures-emission-du-3-mars-2008.fr.html
   |title= Journal de 20 Heures |access-date=3 March 2008
   |at=approximately minute 30 of the TV news broadcast
   |work= Institut national de l'audiovisuel
   |author1=Gérard Poirier   |author2=Foued Berahou
   |date=3 March 2008}}</ref> but one manufacturer later estimated the longevity of its CD-Rs with a gold-sputtered layer to be as high as 100 years.<ref>{{cite web
   |url=http://delkin.com/i-5937134-archival-gold-cd-r-300-year-disc-binder-of-10-discs-with-scratch-armor-surface.html
   |title=Archival Gold CD-R "300 Year Disc" Binder of 10 Discs with Scratch Armor Surface
   |archive-date=27 September 2013 |archive-url=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
   |website=Delkin Devices |publisher=Delkin Devices Inc.}}</ref> Sony's [[proprietary format|proprietary]] [[Optical Disc Archive]]<ref name="SpectraLogicDigitalDataStorageOutlook2017" /> can in 2016 reach a read rate of 250&nbsp;MB/s.<ref name="SonyOpticalDiscArchiveGen2">{{cite web |title=Optical Disc Archive Generation 2 |url=https://pro.sony/s3/cms-static-content/file/49/1237494482649.pdf |website=Optical Disc Archive |publisher=Sony |access-date=15 August 2019 |page=12(World’s First 8-Channel Optical Drive Unit) |date=April 2016}}</ref>

====Solid-state drive====
[[Solid-state drives]] (SSDs) use [[integrated circuit]] assemblies to store data. [[Flash memory]], [[thumb drive]]s, [[USB flash drive]]s, [[CompactFlash]], [[SmartMedia]], [[Memory Stick]]s, 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&nbsp;Mbit/s up to 6&nbsp;Gbit/s. Available SSDs have become more capacious and cheaper.<ref>{{cite journal
   |title=Solid-State Drives (SSDs) |journal=Proceedings of the IEEE
   |author1=R. Micheloni |author2=P. Olivo
   |volume=105 |issue=9 |pages=1586–88 |year=2017
   |doi=10.1109/JPROC.2017.2727228 }}</ref><ref name=PCMagBest/> Flash memory backups are stable for fewer years than hard disk backups.<ref name="ForbesKeepingDataLongTime" />

====Remote backup service====
[[Remote backup service]]s 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.<ref name="DellRemoteBackup">{{cite web
   |url=https://www.emc.com/corporate/glossary/remote-backup.htm
   |title=Remote Backup |work=EMC Glossary |publisher=Dell, Inc
   |access-date=8 May 2018
   |quote=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.}}</ref> Cloud-based backup (through services like or similar to [[Google Drive]], and [[Microsoft OneDrive]]) provides a layer of data protection.<ref name="PCWorldHardCoreDataPreservation" /> 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,<ref name="PCWorldHardCoreDataPreservation" /> 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.<ref name="StackpoleSoftware07">{{cite book |url=https://books.google.com/books?id=gjAhVzuV7k0C&pg=PA164 |title=Software Deployment, Updating, and Patching |author=Stackpole, B. |author2=Hanrion, P. |publisher=CRC Press |pages=164–165 |year=2007 |isbn=978-1-4200-1329-0 |access-date=8 May 2018}}</ref><ref name="GnanasundaramInfo12">{{cite book |url=https://books.google.com/books?id=PU7gkW9ArxIC&pg=PA255 |title=Information Storage and Management: Storing, Managing, and Protecting Digital Information in Classic, Virtualized, and Cloud Environments |editor=Gnanasundaram, S. |editor2=Shrivastava, A. |publisher=John Wiley and Sons |page=255 |year=2012 |isbn=978-1-118-23696-3 |access-date=8 May 2018}}</ref>

====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 [[Storage area network|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 [[Computer virus|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 data protection|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.