Excessive redundant redundancies

Definitions

Excessive Redundant Redundancies

noun

pl. -·cies

  1. the state or quality of being redundant; superfluity
  2. a redundant quantity; overabundance
  3. the use of redundant words
  4. the part of a redundant statement that is superfluous
  5. Brit. discharge from a job or employment because of not being needed; dismissal

Origin of redundancy

Classical Latin redundantia
Excessive Redundant Redundancies

noun

pl. re·dun·dan·cies

  1. The state of being redundant.
  2. Something redundant or excessive; a superfluity.
  3. Repetition of linguistic information inherent in the structure of a language, as singularity in the sentence It works.
  4. Excessive wordiness or repetition in expression.
  5. Chiefly British a. The state or fact of being unemployed because work is no longer offered or considered necessary.b. A dismissal of an employee from work for being no longer necessary; a layoff.
  6. Electronics Duplication or repetition of elements in electronic equipment to provide alternative functional channels in case of failure.
  7. Repetition of parts or all of a message to circumvent transmission errors.
  8. Genetics See degeneracy.

Usage Note: The usages that critics have condemned as redundancies fall into several classes. Some expressions, such as old adage, mental telepathy, and VAT tax have become fixed expressions and seem harmless enough.

In some cases, such as consensus of opinion and hollow tube, the use of what is regarded as an unnecessary modifier or qualifier can sometimes be justified on the grounds that it in fact makes a semantic contribution.

Thus a hollow tube can be distinguished from one that has been blocked up with deposits, and a consensus of opinion can be distinguished from a consensus of judgments or practices. Some locutions, such as close proximity, have been so well established that criticizing them may seem petty.

Excessive Redundant RedundanciesNoun

(plural redundancies)

  • cyclic redundancy check/CRC
  • redundancy check
  • Common Access Redundancy Protocol

Excessive Redundant Redundancies

Synonyms

SentencesSentence examples

Sentence Examples

  • The plan should also offer redundancy, such as training backup employees to handle tasks in case one employee is no longer available.
  • That the Baltic Stream must be a surface current, because it originates from a redundancy of fresh water.
  • In fact, the great blemishes of In Memoriam, its redundancy and the dislocation of its parts, were largely due to the desultory manner of its composition.
  • He was famed in antiquity for the richness and splendour of his imagination and his style, although Quintilian censures his redundancy and Hermogenes remarks on the excessive sweetness that results from his abundant use of epithets.
  • Curiously enough, it is from Schleiermacher's philosophical ethics that a threefold division – the Chief Good, Virtues, and Duty or the Law – passed into almost all text-books of Christian Ethics, till recently a rebellion rose against it on the ground of redundancy and overlapping.

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Redundancy: When Too Much is Just Right

Redundancy is indispensable in the world of information technology. Of course, redundancy is not welcome in every aspect of life. If your company doesn’t need you anymore and makes you “redundant”, you’ll have to look for another job.

Poorly written text may be credited to the Department of Redundancy Department. The concept of redundancy is that there is too much, an excess, more than is needed, a superfluity, a superabundance.

But in information technology or aviation engineering, that can be a very good thing.

Failure Is an Option

A Boeing 747 can fly safely on a single engine.  So why did company engineers put four of them on the airplane?  Just in case.

Before June 24, 1982, aviation experts believed that there was a ridiculously low chance that all four engines on a Boeing 747 could fail simultaneously.

But that’s exactly what happened when, at 37,000 feet over the Indian Ocean, a British Airways flight lost all four engines and continued for 80 nautical miles in unpowered flight before the engines restarted. The culprit was volcanic ash.

The story is recounted in a fascinating technical paper about redundancy in engineering written by John Downer and published in May 2009. The paper is called “When Failure is an Option: Redundancy, reliability and  regulation in complex technical systems”, and it is well worth reading.

Downer says that “redundancy is the single most important engineering tool for designing, implementing, and – importantly – proving reliability in all complex, safety-critical technologies”. He tells how the computing pioneer Jon von Neumann discussed the idea in his writings in 1956.

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And he quotes Yale sociology Charles Parrow, who wrote:  “Two engines are better than one; four better than two.”

Any IT professional should be happy when a backup component takes over after the primary one fails. That means that the redundant system is doing its job. As Downer explains, “An element is redundant if it contains backups to do its work if it fails; a system is redundant if it contains redundant elements.” But as in the case of the 1982 Boeing 747 flight, even that may not be enough.

Single Points of Failure

Redundant systems may be all the rage in the world of IT, but a design that contains a single point of failure is anathema. A single point of failure (SPOF) means that an entire system can go down if that one element of the system fails. The concept is commonly bandied about in IT circles, but it’s just as applicable to any engineered system.

If you are in an airplane that has only one engine and that engine dies, you’re in real trouble. The same applies to an IT system without redundancy. Techopedia explains it this way: “Highly reliable systems are designed without SPOFs. This means that failure of a component, system or site does not halt system or operational functions.”

It just makes sense to have a spare on hand when you need it. You carry around a spare tire in your car. Stores with point-of-sale cash registers keep extra rolls of printing paper close by as bench stock.

And you can probably think of many other areas of life where backups and redundancy make it possible to continue even after a single element fails. The same is true for critical elements in IT.

Systems that don’t provide redundancy and leave users vulnerable to single points of failure are just examples of poor system design.

Different Scopes of Failure

In order to develop a sound redundancy plan, it’s a good idea to anticipate how things could fail. Of course, now matter how well we prepare, Murphy’s Law could take over and things could fall apart. But just as in our recent blog post about proactive maintenance, being proactive about potential failures is going to pay off in the long run.

Redundancy (engineering)

Duplication of critical components to increase reliability of a system
For other uses, see Redundancy.

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed.Find sources: “Redundancy” engineering – news · newspapers · books · scholar · JSTOR (February 2014) (Learn how and when to remove this template message)

Common redundant power supply
Redundant subsystem “B”
Extensively redundant rear lighting installation on a Thai tour bus

In engineering, redundancy is the duplication of critical components or functions of a system with the intention 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 expected to fail independently, the probability of all three failing is calculated to be extraordinarily small; often outweighed by other risk factors, such as human error.

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]

Forms of redundancy

In computer science, there are four major forms of redundancy,[5] these are:

  • 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
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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.

Series (A) and parallel (B) systems and their combination (C).[6]

Parallel and combined systems demonstrate different level of redundancy. The models are subject of studies in reliability and safety engineering.

Function of redundancy

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]

Disadvantages

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

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.

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.

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.

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Calculating the probability of system failure

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.

See also

  • Degeneracy
  • Common cause and special cause (statistics)
  • Data redundancy
  • Double switching
  • Fault tolerance – Resilience of systems to component failures or errors
  • Radiation hardening – Processes and techniques used for making electronic devices resistant to ionizing radiation
  • Factor of safety – Factor by which an engineered system's capacity is higher than the expected load to ensure safety in case of error or uncertainty
  • Reliability engineering – Sub-discipline of systems engineering that emphasizes dependability in the lifecycle management of a product or a system
  • Reliability theory of aging and longevity
  • Safety engineering – Engineering discipline which assures that engineered systems provide acceptable levels of safety
  • Reliability (computer networking)
  • MTBF
  • N+1 redundancy

References

  1. ^ Redundancy Management Technique for Space Shuttle Computers (PDF), IBM Research
  2. ^ 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.

  3. ^ “The Aerospace Corporation | Assuring Space Mission Success”. Aero.org. 2014-05-20. Retrieved 2014-06-01.
  4. ^ a b Scott D. Sagan (March 2004). “Learning from Normal Accidents” (PDF). Organization & Environment.

    Archived from the original (PDF) on 2004-07-14.

  5. ^ Koren, Israel; Krishna, C. Mani (2007). Fault-Tolerant Systems. San Francisco, CA: Morgan Kaufmann. p. 3. ISBN 978-0-12-088525-1.
  6. ^ Kokcharov I. Structural Safety http://www.kokch.kts.ru/me/t6/SIA_6_Structural_Safety.pdf

External links

  • 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.

Redundancy sentence examples

  • That the Baltic Stream must be a surface current, because it originates from a redundancy of fresh water.
  • In fact, the great blemishes of In Memoriam, its redundancy and the dislocation of its parts, were largely due to the desultory manner of its composition.
  • The plan should also offer redundancy, such as training backup employees to handle tasks in case one employee is no longer available.
  • He was famed in antiquity for the richness and splendour of his imagination and his style, although Quintilian censures his redundancy and Hermogenes remarks on the excessive sweetness that results from his abundant use of epithets.
  • redundancy pay is by any measure quite low.
  • Curiously enough, it is from Schleiermacher's philosophical ethics that a threefold division – the Chief Good, Virtues, and Duty or the Law – passed into almost all text-books of Christian Ethics, till recently a rebellion rose against it on the ground of redundancy and overlapping.
  • People come to her when they are facing major upheaval in their lives such as redundancy or divorce.
  • When do schemes for enhanced redundancy payments become contractual?
  • To get anything decent, we are going to edge or go into deco, that also means suitable redundancy.
  • dismissal and/or redundancy claims.
  • Using staff flexibility (within reasonable limits) should maximize opportunities to avoid redundancy dismissals.
  • dismissals for redundancy, even where the employer has gone into administration.
  • Those facing the possibility of redundancy or mid life career doldrums will gain in equal measures too.
  • New guidance on the revised redundancy arrangements in the NHS has now been published by NHS employers.

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