# Fault tolerance
## MicroSim spec
### Parameters (tunable controls)
- `Redundant copies` · 1–5 · parallel replicas voting on the result
- `Fault rate` · 0–0.5 · per-step probability any one replica fails
- `Voting threshold` · 1–5 · replicas that must agree to mask a fault
### What animates
Replica boxes flip to faulted; a voter highlights whether the system still outputs correctly.
### Learning objective
Show how redundancy and voting mask individual component faults.
## Links (Wikipedia order)
<!-- injected from _registry/childlinks/Fault_tolerance.json (2026-07-30T02:09:12Z) -->
`ACM_Computing_Surveys` · [[Aerospace_engineering]] · `Airbag` · `Aircraft` · `Antonín_Svoboda_(computer_scientist)` · [[Arthur_David_Hall_III]] · [[Availability]] · [[Benjamin_S._Blanchard]] · [[Biological_systems_engineering]] · `Brian_Randell` · `Built-in_self-test` · [[Business_process]] · `Chernobyl_disaster` · `Circuit_breaker_design_pattern` · `Client_(computing)` · [[Cognitive_systems_engineering]] · `Collider` · `Computer_accessibility` · [[Computer_engineering]] · [[Computer_hardware]] · `Computer_memory` · [[Configuration_management]] · [[Control_engineering]] · `Control_reconfiguration` · [[Corrosion]] · `Crash-only_software` · `Crossbar_switch` · `Czechoslovakia` · `Damage_tolerance` · `Data_loss` · `Data_redundancy` · [[Decision-making]] · `Defence_in_depth` · [[Derek_Hitchins]] · [[Design_review]] · `Drum_memory` · `Dual_modular_redundancy` · [[Earth_systems_engineering_and_management]] · `Ecological_resilience` · [[Electrical_engineering]] · `Elegant_degradation` · [[Enterprise_systems_engineering]] · `Error-tolerant_design` · [[Error_detection_and_correction]] · `Fail-fast_system` · `Fail-safe` · `Failing_badly` · `Failover` · `Failure_semantics` · `Failure_transparency` · `Fall_back_and_forward` · [[Fatigue_(material)]] · `Firewall_(computing)` · `Forward_compatibility` · [[Function_model]] · `General_Electric` · `Graceful_exit` · [[Graph_theory]] · `Gravity` · `HTML` · [[Harold_Chestnut]] · `Hazard` · [[Health_systems_engineering]] · `Hot_swapping` · `Human_error` · `Human_spaceflight` · `IBM` · [[IDEF]] · [[Industrial_engineering]] · `Instrumentation_(computer_programming)` · `Intrusion_tolerance` · [[James_S._Albus]] · `JavaScript` · [[John_N._Warfield]] · [[John_von_Neumann]] · [[Joseph_Francis_Shea]] · `Just-in-time_compilation` · [[Kathleen_Carley]] · [[Katia_Sycara]] · `List_of_system_quality_attributes` · `Lockstep_(computing)` · [[Manuela_M._Veloso]] · [[Mathematical_optimization]] · `Mean_time_to_repair` · `Minimalism_(computing)` · `Mission_critical` · `NASA` · `NonStop_(server_computers)` · `Nuclear_power` · `Nuclear_power_plant` · `Nuclear_reactor` · `Online_transaction_processing` · [[Operations_research]] · `Outreach` · `Parallel_computing` · `Performance_engineering` · `Pin_(computer_program)` · [[Probability]] · `Progressive_enhancement` · [[Project_management]] · `Protection_mechanism` · `Quality_function_deployment` · `Quality_management` · `Quorum` · `RAID` · `RAM_parity` · [[Radhika_Nagpal]] · [[Redundancy_(engineering)]] · [[Reliability_engineering]] · `Replication_(computing)` · [[Requirements_engineering]] · `Resilience_(engineering_and_construction)` · `Risk_management` · `Robert_E._Machol` · [[Robustness_(computer_science)]] · `Rollback_(data_management)` · `Ruzena_Bajcsy` · `SAPO_(computer)` · [[Safety_engineering]] · `Satellite` · `Saturn_V` · `Seat_belt` · `Self-management_(computer_science)` · `Simon_Ramo` · `Single_point_of_failure` · `Software` · `Software_brittleness` · [[Software_engineering]] · `Space_probe` · `Spare_part` · `Springer_Science+Business_Media` · [[Stanford_torus]] · `Stochastic` · `Stratus_Technologies` · `Synchronization_(computer_science)` · [[System]] · [[System_dynamics]] · `System_integration` · [[System_of_systems_engineering]] · `Systems_analysis` · `Systems_development_life_cycle` · [[Systems_engineering]] · `Systems_modeling` · `Tandem_Computers` · `Triple_modular_redundancy` · `Unisys` · `Uptime` · `User_interface_design` · `V-model` · `Verification_and_validation` · `Voyager_program` · `Web_browser` · `Wernher_von_Braun` · `Western_Electric` · `Wolt_Fabrycky` · [[Work_breakdown_structure]]
<!-- GIFPLATE:BEGIN v1.0 g16 — Commons hotlink; do not hand-edit inside -->
## Images
<figure class="wt-gifplate">
<img src="https://commons.wikimedia.org/wiki/Special:FilePath/Simple_Pendulum_Oscillator.gif" alt="Perturbation Recovery" loading="lazy" decoding="async">
<figcaption><strong>Perturbation Recovery</strong> — Illustrate system returning to normal operation after perturbation.<br>
<span class="wt-credit">Wikimedia Commons · <strong>licence pending verification</strong> (run <code>g17_gif_verify.py</code> on a networked lane) · <a href="https://commons.wikimedia.org/wiki/File:Simple_Pendulum_Oscillator.gif">Details</a></span></figcaption>
</figure>
*This page has no interactive build yet, so the plate carries the concept. It is the first thing that moves on [[Fault_tolerance]].*
<!-- GIFPLATE:END -->
## From the Real GENERATIVE library (beauty pass)
*Fault tolerance — image hotlinked from Wikimedia Commons (via the Real G.E.N.E.R.A.T.I.V.E. course library, Engineering room). [Details & license](https://commons.wikimedia.org/wiki/File:Twitter_M2_mobile_website.png).*
> Fault tolerance is the ability of a system to maintain proper operation despite failures or faults in one or more of its components. This capability is essential for high-availability, mission-critical, or even life-critical systems. ([Wikipedia](https://en.wikipedia.org/wiki/Fault_tolerance))
<!-- BEAUTY-PASS-MEDIA:END -->
> p5.js MicroSim stub · part of Systems Engineering · [Wikipedia source](https://en.wikipedia.org/wiki/Fault_tolerance)
## Concept summary
Fault tolerance is the ability of a [[System|system]] to contain the propagation of faults (e.g. failed [[Transistor|transistor]], shorted connector, intermittent data bus).
## Build checklist
- [ ] Claim it: set `status: in-progress` + `lease` + `leased_at`
- [ ] Write the child page explaining the concept (tie it back to Systems Engineering)
- [ ] Finalize parameter ranges and defaults
- [ ] Implement the p5.js sketch (drawing + control regions)
- [ ] Add caption + the learning objective on the page
- [ ] Set `status: done`
## p5.js sketch
```javascript
// MicroSim: Fault tolerance
const ARTICLE = "Fault_tolerance";
let p1, p2, p3;
function setup() {
createCanvas(720, 520);
pixelDensity(2);
// reliability-sim sim — create the three sliders described above:
// Redundant copies (1–5), Fault rate (0–0.5), Voting threshold (1–5).
// TODO: build labelled sliders in the control region (below the drawing region).
}
function draw() {
background(248);
// TODO: read p1/p2/p3; render the reliability-sim in the drawing region and respond live.
// TODO: HUD — title + en.wikitube.io/wiki/Fault_tolerance + control hints + live readouts.
}
```
---
Back to Systems Engineering
---
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## Semiotic profile
> *The semiotic universals this article invokes, machine-derived from the crossref — **unverified** (born so). Populated 2026-07-06 for the Systems room.*
**Universals (6):** 🟡 system (30) · 🟡 architecture (3) · 🟢 feedback (2) · 🟢 threshold (2) · 🟢 emergence (1) · 🟢 probability (1)
**Enter by sign:** Systems Semiotic Gateway · Alphabetum · Icon Registry · ← Systems Portal
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## Wikipedia : Wikitube
**Strict pair:** [Wikipedia](https://en.wikipedia.org/wiki/Fault_tolerance) : [Wikitube](https://en.wikitube.io/wiki/Fault_tolerance)
## Previous hub tags
Tree parents: [[Graph_theory]] · [[Information_theory]] · [[Reliability_engineering]] · [[System_dynamics]] · [[Systems_engineering]].
Legacy hubs: none.
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*Sources: 2 legacy notes. Minted wave 1, 2026-07-30 (v1.6 order).*