Editing Backup (section)

====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>