N+1 redundancy

N+1 redundancy

N+1 redundancy is a form of resilience that ensures system availability in the event of component failure. Components (N) have at least one independent backup component (+1). The level of resilience is referred to as active/passive or standby as backup components do not actively participate within the system during normal operation. The level of transparency (disruption to system availability) during failover is dependent on a specific solution, though degradation to system resilience will occur during failover. It is also possible to have N+1 redundancy with active-active components, in such cases the backup component will remain active in the operation even if all other components are fully functional, however the system will be able to perform in the event that one component is faulted and recover from a single component failure. An active-active approach is considered superior in terms of performance and resiliency.

Examples of N+1 redundancy:

  • Connecting devices (server etc) in dual switch SAN fabrics employ a discrete path to each switch. Only one path is active at any given time, resiliency is provided by the availability of an additional path if the active path becomes unavailable.
  • Data centre power generators that activate when the normal power source is unavailable.

1+1 redundancy typically offers the advantage of additional failover transparency in the event of component failure. The level of resilience is referred to as active/active or hot as backup components actively participate with the system during normal operation. Failover is generally transparent (disruption to system availability) as failover does not actually occur (just degradation to system resilience) as the backup components were already active within the system.

Examples of 1+1 redundancy:

  • Dual active power supplies in a server.
  • Mirrored hard drives within a server/PC system.

Applications

Redundant systems are often used in data centers to ensure that computer systems continue without service interruption. Other common implementations include aerospace, where redundant systems are used to improve safety and integrity of spacecraft, and automobiles, where the emergency brake is available in a car as a redundant component in case of failure of the main brake systems.

See also


Wikimedia Foundation. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • redundancy — re‧dun‧dan‧cy [rɪˈdʌndənsi] noun redundancies PLURALFORM [countable, uncountable] especially BrE HUMAN RESOURCES when someone loses their job in a company because the job is no longer needed: • Over 2000 car workers now face redundancy. • Sev …   Financial and business terms

  • Redundancy (information theory) — Redundancy in information theory is the number of bits used to transmit a message minus the number of bits of actual information in the message. Informally, it is the amount of wasted space used to transmit certain data. Data compression is a way …   Wikipedia

  • Redundancy — may refer to: Redundancy (engineering) Redundancy (information theory) Redundancy (language) Redundancy (total quality management) Redundancy (user interfaces) Data redundancy Gene redundancy Logic redundancy Redundant acronym syndrome syndrome… …   Wikipedia

  • redundancy — I noun duplication, excess, excessiveness, immoderation, inordinacy, inordinate amount, needlessness, nimiety, overplus, oversupply, pleonasm, recurrence, redundance, redundantia, reiteration, repetition, restatement, retelling, superabundance,… …   Law dictionary

  • redundancy payment — UK US noun [C] (also redundancy pay [U]) ► HR money that a company pays to workers who have lost their jobs because they are no longer needed: eligible for/entitled to a redundancy payment »An employee becomes eligible for a redundancy payment… …   Financial and business terms

  • redundancy — • ‘She is lively and vital enough to be a member of a terrorist gang.’ ‘Lively and vital,’ said Harvey, ‘lively and vital one of these words is redundant.’ Muriel Spark, 1984. English idiom is characterized by redundancy, or apparent redundancy,… …   Modern English usage

  • redundancy payments — Whilst an employer may offer more under the employment agreement or ex gratia, the minimum statutory entitlement redundancy payments under the Employment Rights Act 1996 are as follows: 0.5 of a week s pay per year of service between 18 and 21; 1 …   Law dictionary

  • redundancy package — UK US noun [C] ► HR all the payments and advantages that a company gives to workers who have lost their jobs because they are no longer needed: »If the redundancy package is very generous many staff will opt for that and not even consider… …   Financial and business terms

  • Redundancy — См. Резервирование Термины атомной энергетики. Концерн Росэнергоатом, 2010 …   Термины атомной энергетики

  • redundancy — theory of truth …   Philosophy dictionary

  • redundancy — *verbiage, tautology, pleonasm, circumlocution, periphrasis Analogous words: wordiness, verbosity, prolixity, diffuseness (see corresponding adjectives at WORDY): inflatedness or inflation, turgidity, tumidity, flatulence (see corresponding… …   New Dictionary of Synonyms

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”