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n menu Main menu move to sidebar hide Navigation Main page Contents Current events Random article About Wikipedia Contact us Contribute Help Learn to edit Community portal Recent changes Upload file Special pages Search Search Appearance Donate Create account Log in Personal tools Donate Create account Log in Contents move to sidebar hide (Top) 1 Forms of redundancy Toggle Forms of redundancy subsection 1.1 Dissimilar redundancy 1.2 Geographic redundancy 2 Functions of redundancy 3 Disadvantages 4 Voting logic 5 Calculating the probability of system failure 6 Redundancy and high availability 7 See also 8 References 9 External links Toggle the table of contents Redundancy (engineering) 15 languages العربية Català Deutsch Español فارسی Français Italiano 日本語 한국어 Português Română Русский Українська 粵語 中文 Edit links Article Talk English Read Edit View history Tools Tools move to sidebar hide Actions Read Edit View history General What links here Related changes Upload file Permanent link Page information Cite this page Get shortened URL Print/export Download as PDF Printable version In other projects Wikimedia Commons Wikidata item Appearance move to sidebar hide From Wikipedia, the free encyclopedia Duplication of critical components to increase reliability of a system For other uses, see Redundancy . Common redundant power supply Redundant subsystem "B" In engineering and systems theory , redundancy is the intentional duplication of critical components or functions of a system with the goal of increasing reliability of the system , usually in the form of a backup or fail-safe , or to improve actual system performance, such as in the case of GNSS receivers, or multi-threaded computer processing. In many safety-critical systems , such as fly-by-wire and hydraulic systems in aircraft , some parts of the control system may be triplicated, [ 1 ] which is formally termed triple modular redundancy (TMR). An error in one component may then be out-voted by the other two. In a triply redundant system, the system has three sub components, all three of which must fail before the system fails. Since each one rarely fails, and the sub components are designed to preclude common failure modes (which can then be modelled as independent failure), the probability of all three failing is calculated to be extraordinarily small; it is often outweighed by other risk factors, such as human error . Electrical surges arising from lightning strikes are an example of a failure mode which is difficult to fully isolate, unless the components are powered from independent power busses and have no direct electrical pathway in their interconnect (communication by some means is required for voting). Redundancy may also be known by the terms "majority voting systems" [ 2 ] or "voting logic". [ 3 ] A suspension bridge's numerous cables are a form of redundancy. Redundancy sometimes produces less, instead of greater reliability –  it creates a more complex system which is prone to various issues, it may lead to human neglect of duty, and may lead to higher production demands which by overstressing the system may make it less safe. [ 4 ] Redundancy is one form of robustness as practiced in computer science . Geographic redundancy has become important in the data center industry, to safeguard data against natural disasters and political instability (see below). Forms of redundancy [ edit ] In computer science, there are four major forms of redundancy: [ 5 ] Hardware redundancy, such as dual modular redundancy and triple modular redundancy Information redundancy, such as error detection and correction methods Time redundancy, performing the same operation multiple times such as multiple executions of a program or multiple copies of data transmitted Software redundancy such as N-version programming A modified form of software redundancy, applied to hardware may be: Distinct functional redundancy, such as both mechanical and hydraulic braking in a car. Applied in the case of software, code written independently and distinctly different but producing the same results for the same inputs. Structures are usually designed with redundant parts as well, ensuring that if one part fails, the entire structure will not collapse. A structure without redundancy is called fracture-critical , meaning that a single broken component can cause the collapse of the entire structure. Bridges that failed due to lack of redundancy include the Silver Bridge and the Interstate 5 bridge over the Skagit River . Parallel and combined systems demonstrate different level of redundancy. The models are subject of studies in reliability and safety engineering. [ 6 ] Dissimilar redundancy [ edit ] Unlike traditional redundancy, which uses more than one of the same thing, dissimilar redundancy uses different things. The idea is that the different things are unlikely to contain identical flaws. The voting method may involve additional complexity if the two things take different amounts of time. Dissimilar redundancy is often used with software, because identical software contains identical flaws. The chance of failure is reduced by using at least two different types of each of the following processors, operating systems, software, sensors, types of actuators (electric, hydraulic, pneumatic, manual mechanical, etc.) communications protocols, communications hardware, communications networks, communications paths [ 7 ] [ 8 ] [ 9 ] Geographic redundancy [ edit ] Geographic redundancy corrects the vulnerabilities of redundant devices deployed by geographically separating backup devices. Geographic redundancy reduces the likelihood of events such as power outages , floods , HVAC failures, lightning strikes, tornadoes , building fires, wildfires , and mass shootings disabling most of the system if not the entirety of it. Geographic redundancy locations can be more than 621 miles (999 km) continental , [ 10 ] more than 62 miles apart and less than 93 miles (150 km) apart, [ 10 ] less than 62 miles apart, but not on the same campus, or different buildings that are more than 300 feet (91 m) apart on the same campus. The following methods can reduce the risks of damage by a fire conflagration : large buildings at least 80 feet (24 m) to 110 feet (34 m) apart, but sometimes a minimum of 210 feet (64 m) apart. [ 11 ] [ 12 ] : 9  high-rise buildings at least 82 feet (25 m) apart [ 12 ] : 12  [ 13 ] open spaces clear of flammable vegetation within 200 feet (61 m) on each side of objects [ 14 ] different wings on the same building, in rooms that are separated by more than 300 feet (91 m) different floors on the same wing of a building in rooms that are horizontally offset by a minimum of 70 feet (21 m) with fire walls between the rooms that are on different floors two rooms separated by another room, leaving at least a 70-foot gap between the two rooms there should be a minimum of two separated fire walls and on opposite sides of a corridor [ 10 ] Geographic redundancy is used by Amazon Web Services (AWS), Google Cloud Platform (GCP), Microsoft Azure, Netflix, Dropbox, Salesforce, LinkedIn, PayPal, Twitter, Facebook, Apple iCloud, Cisco Meraki, and many others to provide geographic redundancy, high availability, fault tolerance and to ensure availability and reliability for their cloud services. [ 15 ] As another example, to minimize risk of damage from severe windstorms or water damage, buildings can be located at least 2 miles (3.2 km) away from the shore, with an elevation of at least 5 feet (1.5 m) above sea level. For additional protection, they can be located at least 100 feet (30 m) away from flood plain areas. [ 16 ] [ 17 ] Functions of redundancy [ edit ] The two functions of redundancy are passive redundancy and active redundancy . Both functions prevent performance decline from exceeding specification limits without human intervention using extra capacity. Passive redundancy uses excess capacity to reduce the impact of component failures. One common form of passive redundancy is the extra strength of cabling and struts used in bridges. This extra strength allows some structural components to fail without bridge collapse. The extra strength used in the design is called the margin of safety. Eyes and ears provide working examples of passive redundancy. Vision loss in one eye does not cause blindness but depth perception is impaired. Hearing loss in one ear does not cause deafness but directionality is lost. Performance decline is commonly associated with passive redundancy when a limited number of failures occur. Active redundancy eliminates performance declines by monitoring the performance of individual devices, and this monitoring is used in voting logic. The voting logic is linked to switching that automatically reconfigures the components. Error detection and correction and the Global Positioning System (GPS) are two examples of active redundancy. Electrical power distribution provides an example of active redundancy. Several power lines connect each generation facility with customers. Each power line includes monitors that detect overload. Each power line also includes circuit breakers. The combination of power lines provides excess capacity. Circuit breakers disconnect a power line when monitors detect an overload. Power is redistributed across the remaining lines. [ citation needed ] At the Toronto Airport, there are 4 redundant electrical lines. Each of the 4 lines supply enough power for the entire airport. A spot network substation uses reverse current relays to open breakers to lines that fail, but lets power continue to flow the airport. Electrical power systems use power scheduling to reconfigure active redundancy. Computing systems adjust the production output of each generating facility when other generating facilities are suddenly lost. This prevents blackout conditions during major events such as an earthquake. Disadvantages [ edit ] Charles Perrow , author of Normal Accidents , has said that sometimes redundancies backfire and produce less, not more reliability. This may happen in three ways: First, redundant safety devices result in a more complex system, more prone to errors and accidents. Second, redundancy may lead to shirking of responsibility among workers. Third, redundancy may lead to increased production pressures, resulting in a system that operates at higher speeds, but less safely. [ 4 ] Voting logic [ edit ] Voting logic uses performance monitoring to determine how to reconfigure individual components so that operation continues without violating specification limitations of the overall system. Voting logic often involves computers, but systems composed of items other than computers may be reconfigured using voting logic. Circuit breakers are an example of a form of non-computer voting logic. The simplest voting logic in computing systems involves two components: primary and alternate. They both run similar software, but the output from the alternate remains inactive during normal operation. The primary monitors itself and periodically sends an activity message to the alternate as long as everything is OK. All outputs from the primary stop, including the activity message, when the primary detects a fault. The alternate activates its output and takes over from the primary after a brief delay when the activity message ceases. Errors in voting logic can cause both outputs to be active or inactive at the same time, or cause outputs to flutter on and off. A more reliable form of voting logic involves an odd number of three devices or more. All perform identical functions and the outputs are compared by the voting logic. The voting logic establishes a majority when there is a disagreement, and the majority will act to deactivate the output from other device(s) that disagree. A single fault will not interrupt normal operation. This technique is used with avionics systems, such as those responsible for operation of the Space Shuttle . Calculating the probability of system failure [ edit ] See also: Failure rate and Mean time between failures Each duplicate component added to the system decreases the probability of system failure according to the formula:- p = ∏ i = 1 n p i {\displaystyle {p}=\prod _{i=1}^{n}p_{i}} where: n {\displaystyle n} – number of components p i {\displaystyle p_{i}} – probability of component i failing p {\displaystyle p} – the probability of all components failing (system failure) This formula assumes independence of failure events. That means that the probability of a component B failing given that a component A has already failed is the same as that of B failing when A has not failed. There are situations where this is unreasonable, such as using two power supplies connected to the same socket in such a way that if one power supply failed, the other would too. It also assumes that only one component is needed to keep the system running. Redundancy and high availability [ edit ] This section contains instructions or advice . Wikipedia is not a guidebook; please help rewrite such content to be encyclopedic or move it to Wikiversity , Wikibooks , or Wikivoyage . ( May 2026 ) You can achieve higher availability through redundancy. Let's say you have three redundant components: A, B and C. You can use following formula to calculate availability of the overall system: Availability of redundant components = 1 - (1 - availability of component A) X (1 - availability of component B) X (1 - availability of component C) [ 18 ] [ 19 ] In corollary, if you have N parallel components each having X availability, then: Availability of parallel components = 1 - (1 - X)^ N 10 hosts, each having 50% availability. But if they are used in parallel and fail independently, they can provide high availability. Using redundant components can exponentially increase the availability of overall system. [ 19 ]  For example if each of your hosts has only 50% availability, by using 10 of hosts in parallel, you can achieve 99.9023% availability. Note that redundancy doesn't always lead to higher availability. In fact, redundancy increases complexity which in turn reduces availability. According to Marc Brooker, to take advantage of redundancy, ensure that: [ 20 ] You achieve a net-positive improvement in the overall availability of your system Your redundant components fail independently Your system can reliably detect healthy redundant components Your system can reliably scale out and scale-in redundant components. See also [ edit ] Air gap (networking)  – Network security measure Common cause and special cause (statistics)  – Statistics concept Data redundancy  – Surplus computer data for error correction Double switching Fault tolerance  – Resilience of systems to component failures or errors Radiation hardening  – Making devices resist ionizing radiation Factor of safety  – System strength beyond planned load Reliability engineering  – Sub-discipline of systems engineering that emphasizes dependability Reliability theory of aging and longevity  – Biophysics theory Safety engineering  – Engineering discipline Reliability (computer networking)  – Protocol acknowledgement capability MTBF  – Predicted elapsed time between inherent failures of a system during operation Pages displaying short descriptions of redirect targets N+1 redundancy  – Form of resilience with independent backup components fault-tolerant computer system  – Resilience of systems to component failures or errors Pages displaying short descriptions of redirect targets ZFS  – Copy-on-write file system Byzantine fault  – Fault in a computer system that presents different symptoms to different observers Byzantine Paxos  – Family of protocols for solving consensus Quantum Byzantine agreement  – Quantum version of the Byzantine agreement protocol Two Generals' Problem  – Thought experiment Degeneracy  – Process in biology References [ edit ] ^ Redundancy Management Technique for Space Shuttle Computers (PDF), IBM Research ^ R. Jayapal (2003-12-04). "Analog Voting Circuit Is More Flexible Than Its Digital Version" . elecdesign.com. Archived from the original on 2007-03-03 . Retrieved 2014-06-01 . ^ "The Aerospace Corporation | Assuring Space Mission Success" . Aero.org. 2014-05-20. Archived from the original on 2008-04-10 . Retrieved 2014-06-01 . ^ a b Scott D. Sagan (March 2004). "Learning from Normal Accidents" (PDF) . Organization & Environment . Archived from the original (PDF) on 2004-07-14. ^ Koren, Israel; Krishna, C. Mani (2007). Fault-Tolerant Systems . San Francisco, CA: Morgan Kaufmann. p. 3. ISBN   978-0-12-088525-1 . ^ [1] Smithsonian Institution | Office of Safety, Health, and Environmental Management | Fire Protection and Life Safety Design ManualIndependent Sources | Facilities with a maximum possible fire loss exceeding $ 50 million must have two independent sources of fire protection water. ^ [2] Why Dissimilar Redundant Architectures Are a Necessity for DAL A | Curtis Wright Defense Systems ] ^ [3] Fire Alarm Circuits | A Class X circuit will continue to work with a single open or a single short-circuit by use of a redundant path. ^ [4] Protecting against the power of lightning | to protect against induced surges rather than direct lightning strikes. Feb 1st, 2005 Twisted pair ^ a b c [5] Data Center Site Redundancy | H. M. Brotherton and J. Eric Dietz | Computer Information Technology, Purdue University ^ [6] Factory Mutual Insurance Company | 1-20 Protection Against Exterior Fire Exposure ^ a b [7] National Research Council | Canada | Division Of Building Research | Spatial Separation Of Buildings | November 1959 ^ [8] Tall Building Design Guidelines | City of Toronto | March 2013 | Page 52 | the separation distance between towers on the same site of 25 meters or more ^ [9] Protecting Residences From Wildfires | by Howard E. Moore (General Technical Report PSW-50) | page 30, item 10. ^ [10] On-Premises Cloud Is a Failure. Google Has the Fix | Elias Khnaser | 05/17/2023 ^ https://www.archives.gov/files/records-mgmt/storage-standards-toolkit/file3.pdf Facility Standards for Records Storage Facilities ^ https://www.archives.gov/preservation/storage/presidential-library-standards.html Standards for Permanent Records Storage and Presidential Libraries ^ Sandborn, Peter; Lucyshyn, William (2022). System Sustainment: Acquisition And Engineering Processes For The Sustainment Of Critical And Legacy Systems . World Scientific. ISBN   9789811256868 . ^ a b Trivedi, Kishor S.; Bobbio, Andrea (2017). Reliability and Availability Engineering: Modeling, Analysis, and Applications . Cambridge University Press. ISBN   978-1107099500 . ^ Vitillo, Roberto (23 February 2022). Understanding Distributed Systems, Second Edition: What every developer should know about large distributed applications . Roberto Vitillo. ISBN   978-1838430214 . External links [ edit ] Secure Propulsion using Advanced Redundant Control Using powerline as a redundant communication channel Flammini, Francesco; Marrone, Stefano; Mazzocca, Nicola; Vittorini, Valeria (2009). "A new modeling approach to the safety evaluation of N-modular redundant computer systems in presence of imperfect maintenance". Reliability Engineering & System Safety . 94 (9): 1422– 1432. arXiv : 1304.6656 . doi : 10.1016/j.ress.2009.02.014 . 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Bachrach Albert R. Behnke Peter B. Bennett Paul Bert George F. Bond Robert Boyle Alf O. Brubakk Albert A. Bühlmann John R. Clarke Guybon Chesney Castell Damant Kenneth William Donald William Paul Fife John Scott Haldane Robert William Hamilton Jr. Henry Valence Hempleman Leonard Erskine Hill Brian Andrew Hills Felix Hoppe-Seyler Christian J. Lambertsen Simon Mitchell Charles Momsen Neal W. Pollock John Rawlins Charles Wesley Shilling Edward D. Thalmann Jacques Triger Diving medical research organisations Aerospace Medical Association Divers Alert Network (DAN) Diving Diseases Research Centre (DDRC) Diving Medical Advisory Council (DMAC) European Diving Technology Committee (EDTC) European Underwater and Baromedical Society (EUBS) National Board of Diving and Hyperbaric Medical Technology Naval Submarine Medical Research Laboratory Royal Australian Navy School of Underwater Medicine Rubicon Foundation South Pacific Underwater Medicine Society (SPUMS) Undersea and Hyperbaric Medical Society (UHMS) United States Navy Experimental Diving Unit (NEDU) Law Civil liability in recreational diving Diving regulations Duty of care List of legislation regulating underwater diving Investigation of diving accidents Convention on the Protection of the Underwater Cultural Heritage History of underwater diving History of decompression research and development History of dive computers History of Diving Museum History of scuba diving List of researchers in underwater diving Lyons Maritime Museum Man in the Sea Museum Timeline of atmospheric diving suits Timeline of diving technology Pearling in Western Australia US Navy decompression models and tables Archeological sites SS Commodore USS Monitor Queen Anne's Revenge Whydah Gally Underwater art and artists The Diver Jason deCaires Taylor Engineers and inventors Jerónimo de Ayanz y Beaumont William Beebe Georges Beuchat Giovanni Alfonso Borelli Joseph-Martin Cabirol John R. Clarke Jacques Cousteau Charles Anthony Deane John Deane Louis de Corlieu Auguste Denayrouze Ted Eldred Henry Fleuss Émile Gagnan Karl Heinrich Klingert Peter Kreeft Christian J. Lambertsen Yves Le Prieur John Lethbridge Ernest William Moir Joseph Salim Peress Auguste Piccard Joe Savoie Willard Franklyn Searle Gordon Smith Augustus Siebe Pierre-Marie Touboulic Jacques Triger Historical equipment Aqua-Lung RV Calypso SP-350 Denise Magnesium torch Nikonos Porpoise regulator Standard diving dress Sub Marine Explorer Vintage scuba Diver propulsion vehicles Advanced SEAL Delivery System Cosmos CE2F series Dry Combat Submersible Human torpedo Motorised Submersible Canoe Necker Nymph R-2 Mala-class swimmer delivery vehicle SEAL Delivery Vehicle Shallow Water Combat Submersible Siluro San Bartolomeo Welfreighter Wet Nellie Military and covert operations Raid on Alexandria (1941) Sinking of the Rainbow Warrior Scientific projects 1992 cageless shark-diving expedition Mission 31 Awards and events Hans Hass Award International Scuba Diving Hall of Fame London Diving Chamber Dive Lectures NOGI Awards Women Divers Hall of Fame Incidents Dive boat incidents Sinking of MV Conception Diver rescues Alpazat cave rescue Tham Luang cave rescue Early diving John Day (carpenter) Charles Spalding Ebenezer Watson Freediving fatalities Stephen Keenan Loïc Leferme Audrey Mestre Nicholas Mevoli Natalia Molchanova Offshore diving incidents Byford Dolphin diving bell accident Drill Master diving accident Star Canopus diving accident Stena Seaspread diving accident Venture One diving accident Waage Drill II diving accident Wildrake diving accident Professional diving fatalities Roger Baldwin John Bennett Victor F. Guiel Jr. Francis P. Hammerberg Craig M. Hoffman Peter Henry Michael Holmes Johnson Sea Link accident Edwin Clayton Link Gerard Anthony Prangley Per Skipnes Robert John Smyth Albert D. Stover Richard A. Walker Lothar Michael Ward Joachim Wendler Bradley Westell Arne Zetterström Scuba diving fatalities 1973 Mount Gambier cave diving accident 2026 Dhekunu Kandu cave diving incident Ricardo Armbruster Allan Bridge David Bright Berry L. Cannon Cotton Coulson Cláudio Coutinho E. Yale Dawson Deon Dreyer Milan Dufek Sheck Exley Maurice Fargues Fernando Garfella Palmer Guy Garman Steve Irwin death Jim Jones Henry Way Kendall Artur Kozłowski Yuri Lipski Kirsty MacColl Agnes Milowka François de Roubaix Chris and Chrissy Rouse Dave Shaw Wesley C. Skiles Dewey Smith Rob Stewart Esbjörn Svensson Josef Velek Publications Manuals NOAA Diving Manual U.S. Navy Diving Manual Basic Cave Diving: A Blueprint for Survival Underwater Handbook Bennett and Elliott's physiology and medicine of diving Encyclopedia of Recreational Diving The new science of skin and scuba diving Professional Diver's Handbook Basic Scuba Standards and Codes of Practice Code of Practice for Scientific Diving (UNESCO) DIN 7876 IMCA Code of Practice for Offshore Diving ISO 24801 Recreational diving services — Requirements for the training of recreational scuba divers General non-fiction The Darkness Beckons Goldfinder The Last Dive Shadow Divers The Silent World: A Story of Undersea Discovery and Adventure Research List of Divers Alert Network publications Dive guides Training and registration Diver training Competence and assessment Competency-based learning Refresher training Skill assessment Diver training standard Diving instructor Diving school Occupational 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(IDRCF) International Diving Schools Association (IDSA) International Marine Contractors Association (IMCA) List of diver certification organizations National Oceanic and Atmospheric Administration (NOAA) Nautical Archaeology Society Recreational diver course referral World Recreational Scuba Training Council (WRSTC) Commercial diver certification authorities Australian Diver Accreditation Scheme (ADAS) Commercial diver registration in South Africa Divers Institute of Technology Health and Safety Executive (HSE) Department of Employment and Labour Commercial diving schools Divers Academy International Norwegian diver school Free-diving certification agencies AIDA International (AIDA) Confédération Mondiale des Activités Subaquatiques (CMAS) Performance Freediving International (PI) Scuba Schools International (SSI) Recreational scuba certification agencies American Canadian Underwater Certifications (ACUC) American Nitrox Divers International (ANDI) Association nationale des moniteurs de plongée (ANMP) British Sub-Aqua Club (BSAC) Comhairle Fo-Thuinn (CFT) Confédération Mondiale des Activités Subaquatiques (CMAS) Federación Española de Actividades Subacuáticas (FEDAS) Fédération Française d'Études et de Sports Sous-Marins (FFESSM) Federazione Italiana Attività Subacquee (FIAS) Global Underwater Explorers (GUE) International Association for Handicapped Divers (IAHD) International Association of Nitrox and Technical Divers (IANTD) International Life Saving Federation (ILS) Israeli Diving Federation (TIDF) National Academy of Scuba Educators (NASE) National Association of Underwater Instructors (NAUI) Nederlandse Onderwatersport Bond (NOB) Professional Association of Diving Instructors (PADI) Professional Diving Instructors Corporation (PDIC) Professional Technical and Recreational Diving (ProTec) Rebreather Association of International Divers (RAID) Sub-Aqua Association (SAA) Scuba Diving International (SDI) Scuba Educators International (SEI) Scuba Schools International (SSI) Türkiye Sualtı Sporları Federasyonu (TSSF) United Diving Instructors (UDI) YMCA SCUBA Program Scientific diver certification authorities American Academy of Underwater Sciences (AAUS) CMAS Scientific Committee Technical diver certification agencies American Nitrox Divers International (ANDI) British Sub-Aqua Club (BSAC) Confédération Mondiale des Activités Subaquatiques (CMAS) Diving Science and Technology (DSAT) Federazione Italiana Attività Subacquee (FIAS) International Association of Nitrox and Technical Divers (IANTD) Professional Association of Diving Instructors (PADI) Professional Diving Instructors Corporation (PDIC) Professional Technical and Recreational Diving (ProTec) Rebreather Association of International Divers (RAID) Trimix Scuba Association (TSA) Cave diving Cave Divers Association of Australia (CDAA) Cave Diving Group (CDG) Global Underwater Explorers (GUE) National Speleological Society#Cave Diving Group (CDG) National Association of Underwater Instructors (NAUI) Technical Diving International (TDI) Military diver training centres Defence Diving School Navy Diving Salvage and Training Center Underwater Escape Training Unit Military diver training courses United States Marine Corps Combatant Diver Course Underwater sports Surface snorkeling Finswimming Snorkeling/breath-hold Spearfishing Underwater football Underwater hockey Australia Turkey Underwater rugby Colombia United States Underwater target shooting Breath-hold Aquathlon Apnoea finswimming Freediving Open Circuit Scuba Immersion finswimming Sport diving Underwater cycling Underwater orienteering Underwater photography Rebreather Underwater photography Sports governing organisations and federations International AIDA International Confédération Mondiale des Activités Subaquatiques ) National AIDA Hellas Australian Underwater Federation British Freediving Association British Octopush Association British Underwater Sports Association Comhairle Fo-Thuinn Federación Española de Actividades Subacuáticas Fédération Française d'Études et de Sports Sous-Marins South African Underwater Sports Federation Türkiye Sualtı Sporları Federasyonu Underwater Society of America ) Competitions 14th CMAS Underwater Photography World Championship Underwater Hockey World Championships Underwater Orienteering World Championships Underwater Rugby World Championships Underwater divers Pioneers of diving Eduard Admetlla i Lázaro Aquanaut John Bevan Mary Bonnin Amelia Behrens-Furniss James F. Cahill Jacques Cousteau Billy Deans Dottie Frazier Trevor Hampton Hans Hass Hannes Keller Dick Rutkowski Teseo Tesei Arne Zetterström Underwater scientists archaeologists and environmentalists Michael Arbuthnot Robert Ballard George Bass Mensun Bound Louis Boutan Jeffrey Bozanic Hugh Bradner Cathy Church Eugenie Clark James P. Delgado Sylvia Earle John Christopher Fine George R. Fischer Anders Franzén Honor Frost Fernando Garfella Palmer David Gibbins Graham Jessop Swietenia Puspa Lestari Pilar Luna Robert F. Marx Anna Marguerite McCann Innes McCartney Charles T. Meide Mark M. Newell Lyuba Ognenova-Marinova John Peter Oleson Mendel L. Peterson Richard Pyle Andreas Rechnitzer William R. Royal Margaret Rule Gunter Schöbel Stephanie Schwabe Myriam Seco E. Lee Spence Robert Sténuit Peter Throckmorton Cristina Zenato Scuba record holders Pascal Bernabé Jim Bowden Mark Ellyatt Sheck Exley Nuno Gomes Claudia Serpieri Krzysztof Starnawski Underwater filmmakers and presenters Samir Alhafith David Attenborough Ramón Bravo Jean-Michel Cousteau Richie Kohler Paul Rose Andy Torbet Ivan Tors Andrew Wight James Cameron Underwater photographers Doug Allan Tamara Benitez Georges Beuchat Adrian Biddle Jonathan Bird Eric Cheng Neville Coleman Jacques Cousteau John D. Craig Ben Cropp Bernard Delemotte David Doubilet Candice Farmer John Christopher Fine Rodney Fox Ric Frazier Stephen Frink Peter Gimbel Monty Halls Hans Hass Henry Way Kendall Rudie Kuiter Joseph B. MacInnis Luis Marden Agnes Milowka Noel Monkman Pete Oxford Steve Parish Zale Parry Pierre Petit Leni Riefenstahl Fred Roberts Peter Scoones Brian Skerry Wesley C. Skiles E. Lee Spence Philippe Tailliez Ron Taylor Valerie Taylor Albert Tillman John Veltri Stan Waterman Michele Westmorland John Ernest Williamson J. Lamar Worzel Underwater explorers Caves Graham Balcombe Sheck Exley Martyn Farr Jochen Hasenmayer Jill Heinerth Jarrod Jablonski Brian Kakuk William Hogarth Main Tom Mount Jack Sheppard Bill Stone Reefs Arthur C. Clarke Wrecks Leigh Bishop John Chatterton Clive Cussler Bill Nagle Valerie van Heest Aristotelis Zervoudis Aquanauts Andrew Abercromby Joseph M. Acaba Clayton Anderson Richard R. Arnold Serena Auñón-Chancellor Michael Barratt (astronaut) Robert A. Barth Robert L. Behnken Randolph Bresnik Timothy J. Broderick Justin Brown Berry L. Cannon Scott Carpenter Gregory Chamitoff Steve Chappell Catherine Coleman Robin Cook Craig B. Cooper Fabien Cousteau Philippe Cousteau Timothy Creamer Jonathan Dory Pedro Duque Sylvia Earle Jeanette Epps Sheck Exley Albert Falco Andrew J. Feustel Michael Fincke Satoshi Furukawa Ronald J. Garan Jr. Michael L. Gernhardt Christopher E. Gerty David Gruber Chris Hadfield Jeremy Hansen José M. Hernández John Herrington Paul Hill Akihiko Hoshide Mark Hulsbeck Emma Hwang Norishige Kanai Les Kaufman Scott Kelly Karen Kohanowich Timothy Kopra Dominic Landucci Jon Lindbergh Kjell N. Lindgren Michael López-Alegría Joseph B. MacInnis Sandra Magnus Thomas Marshburn Matthias Maurer K. Megan McArthur Craig McKinley Jessica Meir Simone Melchior Dorothy Metcalf-Lindenburger Andreas Mogensen Karen Nyberg John D. Olivas Takuya Onishi Luca Parmitano Nicholas Patrick Tim Peake Thomas Pesquet Marc Reagan Garrett Reisman Kathleen Rubins Dick Rutkowski Tara Ruttley David Saint-Jacques Josef Schmid Robert Sheats Dewey Smith Steve Squyres Heidemarie Stefanyshyn-Piper Robert Sténuit Hervé Stevenin Nicole Stott James Talacek Daniel M. Tani Robert Thirsk Bill Todd Mark T. Vande Hei Koichi Wakata Rex J. Walheim Shannon Walker John Morgan Wells Joachim Wendler Douglas H. Wheelock Peggy Whitson Dafydd Williams Jeffrey Williams Sunita Williams Reid Wiseman Kimiya Yui Writers and journalists Michael C. Barnette Victor Berge Philippe Diolé Gary Gentile Bret Gilliam Bob Halstead Hillary Hauser Trevor Jackson Steve Lewis John Mattera Rescuers Craig Challen Richard Harris Rick Stanton John Volanthen Frogmen Lionel Crabb Ian Edward Fraser Sydney Knowles James Joseph Magennis Commercial salvors Keith Jessop Science of underwater diving List of researchers in underwater diving Diving physics Metre sea water Neutral buoyancy Underwater acoustics Modulated ultrasound Underwater vision Underwater computer vision Diving physiology Blood shift Cold shock response Diving reflex Equivalent narcotic depth Maximum operating depth Physiological response to water immersion Thermal balance of the underwater diver Underwater vision Work of breathing Decompression theory Decompression models: Bühlmann decompression algorithm Haldane's decompression model Reduced gradient bubble model Thalmann algorithm Thermodynamic model of decompression Varying Permeability Model Equivalent air depth Oxygen window Physiology of decompression Diving environments Underwater exploration Deep-sea exploration Classification List of diving environments by type Altitude diving Benign water diving Confined water diving Deep diving Inland diving Inshore diving Muck diving Night diving Open-water diving Black-water diving Blue-water diving Penetration diving Cave diving Torricellian chamber Ice diving Wreck diving Recreational dive sites Underwater environment Underwater diving environment Impact Environmental impact of recreational diving Low impact diving Other Bathysphere Defense against swimmer incursions Diver detection sonar Offshore survey Rugged compact camera Underwater domain awareness Underwater vehicle Deep-submergence vehicle Aluminaut DSV Alvin American submarine NR-1 Bathyscaphe Archimède FNRS-2 FNRS-3 Harmony class bathyscaphe Sea Pole -class bathyscaphe Trieste II Deepsea Challenger Ictineu 3 JAGO Jiaolong Konsul -class submersible Limiting Factor Russian submarine Losharik Mir Nautile Pisces -class deep submergence vehicle DSV Sea Cliff DSV Shinkai DSV Shinkai 2000 DSV Shinkai 6500 DSV Turtle DSV-5 Nemo Submarine rescue International Submarine Escape and Rescue Liaison Office Submarine Escape and Rescue system (Royal Swedish Navy) McCann Rescue Chamber Submarine rescue ship Deep-submergence rescue vehicle LR5 LR7 MSM-1 Mystic -class deep-submergence rescue vehicle DSRV-1 Mystic DSRV-2 Avalon NATO Submarine Rescue System Priz -class deep-submergence rescue vehicle Russian deep submergence rescue vehicle AS-28 Russian submarine AS-34 ASRV Remora SRV-300 Submarine Rescue Diving Recompression System Type 7103 DSRV URF (Swedish Navy) Submarine escape Escape trunk Submarine escape training facility Submarine Escape Training Facility (Australia) Escape set Davis Submerged Escape Apparatus Momsen lung Steinke hood Submarine Escape Immersion Equipment Special interest groups Artificial Reef Society of British Columbia CMAS Europe Coral Reef Alliance Divers Alert Network Green Fins Finger Lakes Underwater Preserve Association Karst Underwater Research Nautical Archaeology Program Nautical Archaeology Society Naval Air Command Sub Aqua Club PADI AWARE Reef Check Reef Life Survey Rubicon Foundation Save Ontario Shipwrecks SeaKeys Sea Research Society Society for Underwater Historical Research Society for Underwater Technology Underwater Archaeology Branch, Naval History & Heritage Command Neutral buoyancy facilities for Astronaut training Neutral Buoyancy Laboratory Neutral buoyancy pool Neutral buoyancy simulation as a training aid Neutral Buoyancy Simulator Space Systems Laboratory Yuri Gagarin Cosmonaut Training Center Other Nautilus Productions Helicopter Aircrew Breathing Device Scuba diving therapy Seabed mining Category Commons Glossary Indexes: Dive sites Divers Diving Outline Portal Retrieved from " https://en.wikipedia.org/w/index.php?title=Redundancy_(engineering)&oldid=1353589172 " Categories : Engineering concepts Reliability engineering Safety Fault-tolerant computer systems Hidden categories: Articles with short description Short description is different from Wikidata All articles with unsourced statements Articles with unsourced statements from October 2019 Articles needing cleanup from May 2026 All pages needing cleanup Articles containing how-to sections Pages displaying short descriptions of redirect targets via Module:Annotated link This page was last edited on 11 May 2026, at 04:23  (UTC) . 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