System Resilience and Stability Index Calculator

ANA›Life Services Authority›National Calculator Authority›System Resilience and Stability Index Calculator

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System Resilience and Stability Index Calculator

Calculate the composite System Resilience and Stability Index (SRSI) using redundancy level, mean time to recovery (MTTR), failure rate (λ), and average system load. The index ranges from 0 (no resilience) to 100 (perfect resilience).

Redundancy Level (N) — number of redundant components (1 = no redundancy, max 10)

Mean Time To Recovery — MTTR (hours, > 0)

Mean Time Between Failures — MTBF (hours, > MTTR)

Average System Load (%) — operational load percentage (1–100)

Component Diversity Score (0–1) — architectural/vendor diversity (0 = homogeneous, 1 = fully diverse)

Calculate SRSI

Fill in the fields above and click Calculate.

function sysCalc() { // --- Read inputs --- const N = parseFloat(document.getElementById('sys-redundancy').value); const mttr = parseFloat(document.getElementById('sys-mttr').value); const mtbf = parseFloat(document.getElementById('sys-mtbf').value); const load = parseFloat(document.getElementById('sys-load').value); const diversity = parseFloat(document.getElementById('sys-diversity').value);

const resultDiv = document.getElementById('sys-result');

// --- Validation --- if (isNaN(N) || isNaN(mttr) || isNaN(mtbf) || isNaN(load) || isNaN(diversity)) { resultDiv.innerHTML = '⚠ Please fill in all fields with valid numbers.'; return; } if (N 10 || !Number.isInteger(N)) { resultDiv.innerHTML = '⚠ Redundancy Level must be a whole number between 1 and 10.'; return; } if (mttr ⚠ MTTR must be greater than 0.'; return; } if (mtbf ⚠ MTBF must be greater than MTTR.'; return; } if (load 100) { resultDiv.innerHTML = '⚠ System Load must be between 1 and 100.'; return; } if (diversity 1) { resultDiv.innerHTML = '⚠ Diversity Score must be between 0 and 1.'; return; }

// --------------------------------------------------------------- // FORMULAS // ---------------------------------------------------------------

// 1. Availability (A) — steady-state availability // A = MTBF / (MTBF + MTTR) const A = mtbf / (mtbf + mttr);

// 2. System Availability with N redundant components (parallel model) // A_sys = 1 - (1 - A)^N const A_sys = 1 - Math.pow(1 - A, N);

// 3. Failure Rate λ = 1 / MTBF const lambda = 1 / mtbf;

// 4. Recovery Speed Score (RSS) — normalised inverse of MTTR // RSS = 1 / (1 + ln(1 + MTTR)) → ranges (0,1], penalises long recovery const RSS = 1 / (1 + Math.log(1 + mttr));

// 5. Load Stress Factor (LSF) — penalises high load // LSF = 1 - (load/100)^2 → quadratic penalty const LSF = 1 - Math.pow(load / 100, 2);

// 6. Redundancy Bonus (RB) — logarithmic benefit of extra components // RB = ln(N) / ln(10) → 0 when N=1, 1 when N=10 const RB = Math.log(N) / Math.log(10);

// 7. Composite SRSI (0–100) // SRSI = 100 × [ w1·A_sys + w2·RSS + w3·LSF + w4·RB + w5·diversity ] // Weights: w1=0.35, w2=0.25, w3=0.20, w4=0.10, w5=0.10 (sum=1.00) const w1 = 0.35, w2 = 0.25, w3 = 0.20, w4 = 0.10, w5 = 0.10; const SRSI = 100 * (w1 * A_sys + w2 * RSS + w3 * LSF + w4 * RB + w5 * diversity);

// --- Interpretation --- let grade, color, advice; if (SRSI >= 85) { grade = 'Excellent'; color = '#27ae60'; advice = 'The system demonstrates outstanding resilience and stability. Maintain current architecture and monitor continuously.'; } else if (SRSI >= 70) { grade = 'Good'; color = '#2980b9'; advice = 'The system is reasonably resilient. Consider reducing MTTR or increasing redundancy to reach excellence.'; } else if (SRSI >= 50) { grade = 'Moderate'; color = '#f39c12'; advice = 'Resilience is acceptable but improvements are recommended — reduce load, improve recovery procedures, or add redundancy.'; } else if (SRSI >= 30) { grade = 'Poor'; color = '#e67e22'; advice = 'Significant resilience gaps exist. Prioritise redundancy improvements and faster recovery mechanisms.'; } else { grade = 'Critical'; color = '#c0392b'; advice = 'The system is highly vulnerable. Immediate architectural review and resilience investment are required.'; }

// --- Unavailability in minutes/year --- const unavailMinYear = (1 - A_sys) * 365 * 24 * 60;

resultDiv.innerHTML = ` ### SRSI: ${SRSI.toFixed(2)} / 100 — ${grade}

MetricValue Single-Component Availability (A)${(A * 100).toFixed(4)} % System Availability — ${N} parallel component(s) (A_sys)${(A_sys * 100).toFixed(6)} % Estimated Downtime / Year${unavailMinYear.toFixed(2)} min/yr Failure Rate (λ)${lambda.toFixed(6)} failures/hr Recovery Speed Score (RSS)${RSS.toFixed(4)} Load Stress Factor (LSF)${LSF.toFixed(4)} Redundancy Bonus (RB)${RB.toFixed(4)} Diversity Score${diversity.toFixed(2)}

Recommendation: ${advice}

`; }

#### Formulas Used

1. Single-Component Availability A = MTBF / (MTBF + MTTR)

2. System Availability (N parallel redundant components) A_sys = 1 − (1 − A)N

3. Failure Rate λ = 1 / MTBF

4. Recovery Speed Score RSS = 1 / (1 + ln(1 + MTTR)) — logarithmic penalty for long recovery times

5. Load Stress Factor LSF = 1 − (Load / 100)² — quadratic penalty for high operational load

6. Redundancy Bonus RB = ln(N) / ln(10) — logarithmic benefit of additional redundant components

7. Composite SRSI (0–100) SRSI = 100 × (0.35·A_sys + 0.25·RSS + 0.20·LSF + 0.10·RB + 0.10·Diversity)

#### Assumptions & References

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