RAID Recovery Feasibility Calculator
ANA›Life Services Authority›National Calculator Authority›RAID Recovery Feasibility Calculator
.calc-container { max-width: 640px; margin: 2rem 0; padding: 1.5rem; background: #fff; border: 1px solid #ddd; border-radius: 8px; box-shadow: 0 1px 3px rgba(0,0,0,0.06); font-family: system-ui, -apple-system, sans-serif; } .calc-container h3 { font-family: Georgia, serif; font-size: 1.15rem; color: #1a1a1a; margin-bottom: 1rem; padding-bottom: 0.5rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-row { display: flex; align-items: center; gap: 0.75rem; margin-bottom: 0.75rem; flex-wrap: wrap; } .calc-row label { min-width: 160px; font-size: 0.9rem; color: #333; font-weight: 500; } .calc-row input[type="number"], .calc-row select { flex: 1; min-width: 120px; max-width: 200px; padding: 0.5rem 0.6rem; border: 1px solid #ccc; border-radius: 4px; font-size: 0.9rem; font-family: system-ui, sans-serif; color: #1a1a1a; background: #fafaf8; } .calc-row input:focus, .calc-row select:focus { outline: none; border-color: var(--ac, #3d5a80); box-shadow: 0 0 0 2px rgba(26,74,138,0.12); } .calc-row .unit { font-size: 0.82rem; color: #888; min-width: 30px; } .calc-btn { display: inline-block; margin-top: 0.5rem; padding: 0.55rem 1.5rem; background: var(--ac, #3d5a80); color: #fff; border: none; border-radius: 4px; font-size: 0.9rem; font-weight: 600; cursor: pointer; font-family: system-ui, sans-serif; } .calc-btn:hover { opacity: 0.9; } .calc-result { margin-top: 1.25rem; padding: 1rem 1.25rem; background: #f0f6fc; border-left: 3px solid var(--ac, #3d5a80); border-radius: 0 6px 6px 0; display: none; } .calc-result.visible { display: block; } .calc-result-label { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.06em; color: #666; margin-bottom: 0.25rem; } .calc-result-value { font-size: 1.6rem; font-weight: 700; color: var(--ac, #3d5a80); } .calc-result-detail { font-size: 0.85rem; color: #555; margin-top: 0.5rem; line-height: 1.5; } .calc-note { margin-top: 1rem; font-size: 0.8rem; color: #888; font-style: italic; } .calc-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; margin-top: 0.75rem; } .calc-grid-item { padding: 0.6rem 0.8rem; background: #f8f9fa; border-radius: 4px; border: 1px solid #eee; } .calc-grid-item .label { font-size: 0.75rem; color: #888; text-transform: uppercase; letter-spacing: 0.04em; } .calc-grid-item .value { font-size: 1.1rem; font-weight: 600; color: #1a1a1a; } @media (max-width: 720px) { .calc-row { flex-direction: column; align-items: flex-start; gap: 0.3rem; } .calc-row label { min-width: auto; } .calc-row input[type="number"], .calc-row select { max-width: 100%; width: 100%; } .calc-grid { grid-template-columns: 1fr; } } .calc-chart { margin: 1rem 0; text-align: center; } .calc-chart svg { max-width: 100%; height: auto; } .calc-chart-legend { display: flex; flex-wrap: wrap; justify-content: center; gap: 0.6rem 1.2rem; margin-top: 0.6rem; font-size: 0.8rem; color: #555; } .calc-chart-legend span { display: inline-flex; align-items: center; gap: 0.3rem; } .calc-chart-legend i { display: inline-block; width: 10px; height: 10px; border-radius: 2px; font-style: normal; } .calc-related { max-width: 640px; margin: 2rem 0 1rem; padding: 1.25rem 1.5rem; background: #f8f9fa; border: 1px solid #e8e8e8; border-radius: 8px; } .calc-related h3 { font-family: Georgia, serif; font-size: 1rem; color: #1a1a1a; margin: 0 0 0.75rem; padding-bottom: 0.4rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-related-list { list-style: none; padding: 0; margin: 0 0 0.75rem; display: grid; grid-template-columns: 1fr 1fr; gap: 0.4rem 1.5rem; } .calc-related-list li a { font-size: 0.88rem; color: var(--ac, #3d5a80); text-decoration: none; } .calc-related-list li a:hover { text-decoration: underline; } .calc-browse-all { margin: 0.5rem 0 0; font-size: 0.9rem; font-weight: 600; } .calc-browse-all a { color: var(--ac, #3d5a80); text-decoration: none; } .calc-browse-all a:hover { text-decoration: underline; } @media (max-width: 720px) { .calc-related-list { grid-template-columns: 1fr; } }
RAID Recovery Feasibility Calculator
Estimate the probability of successful RAID data recovery based on your array configuration, number of failed drives, and individual drive health scores.
RAID Level
RAID 0 (Striping) RAID 1 (Mirroring) RAID 5 (Striping + Parity) RAID 6 (Striping + Double Parity) RAID 10 (Stripe of Mirrors)
Total Number of Drives in Array
Number of Failed / Degraded Drives
Estimated Rebuild Time (hours)
Typical: 4–8 hrs per TB per drive at ~150 MB/s
Drive URE Rate (errors per bits read)
Consumer HDD: 1 in 1014 bits Enterprise HDD: 1 in 1015 bits Enterprise SSD: 1 in 1016 bits High-End SSD: 1 in 1017 bits
Drive Capacity (TB per drive)
Calculate Recovery Feasibility Results will appear here.
(function() {
// ── Initialise drive health inputs ────────────────────────────────────────── function raiUpdateDriveInputs() { const total = parseInt(document.getElementById('rai-total-drives').value) || 4; const failed = parseInt(document.getElementById('rai-failed-drives').value) || 0; const container = document.getElementById('rai-health-inputs'); container.innerHTML = '';
if (isNaN(total) || total 0) { const heading = document.createElement('p'); heading.innerHTML = 'Health Score for Each Failed Drive (0 = completely dead, 100 = mostly readable)'; container.appendChild(heading); }
for (let i = 0; i Failed Drive ' + (i + 1) + ' Health (%)' + ''; container.appendChild(div); } }
// ── Main calculation ──────────────────────────────────────────────────────── function raiCalculate() { const resultDiv = document.getElementById('rai-result');
// --- Read inputs --- const raidLevel = parseInt(document.getElementById('rai-raid-level').value); const totalDrives = parseInt(document.getElementById('rai-total-drives').value); const failedCount = parseInt(document.getElementById('rai-failed-drives').value); const rebuildHrs = parseFloat(document.getElementById('rai-rebuild-hours').value); const ureRate = parseFloat(document.getElementById('rai-ure-rate').value); const driveSizeTB = parseFloat(document.getElementById('rai-drive-size-tb').value);
// --- Validation --- const errors = []; if (isNaN(totalDrives) || totalDrives 32) errors.push('Total drives must be between 2 and 32.'); if (isNaN(failedCount) || failedCount totalDrives) errors.push('Failed drives must be between 0 and total drives.'); if (isNaN(rebuildHrs) || rebuildHrs 0) { resultDiv.innerHTML = 'Input Error:' + errors.join('') + ''; return; }
// --- Collect health scores --- const healthScores = []; for (let i = 0; i 100) { resultDiv.innerHTML = 'Health score for drive ' + (i+1) + ' must be 0–100.'; return; } healthScores.push(v); }
// ── Step 1: Fault tolerance (max tolerable failures) ────────────────────── let faultTolerance = 0; let raidName = ''; switch (raidLevel) { case 0: faultTolerance = 0; raidName = 'RAID 0'; break; case 1: faultTolerance = totalDrives - 1; raidName = 'RAID 1'; break; case 5: faultTolerance = 1; raidName = 'RAID 5'; break; case 6: faultTolerance = 2; raidName = 'RAID 6'; break; case 10: faultTolerance = Math.floor(totalDrives / 2); raidName = 'RAID 10'; break; }
// ── Step 2: Structural feasibility ──────────────────────────────────────── // Can the array even be reconstructed given the number of failures? const structurallyFeasible = failedCount 0) { const logSum = healthScores.reduce((acc, h) => acc + Math.log((h / 100) + 1e-9), 0); healthFactor = Math.exp(logSum / healthScores.length); // Clamp to [0, 1] healthFactor = Math.max(0, Math.min(1, healthFactor)); }
// ── Step 5: Rebuild stress factor ───────────────────────────────────────── // Longer rebuilds under load increase risk of additional failures. // Annualised failure rate proxy: assume 4% AFR → hourly rate const afrHourly = 0.04 / 8760; // 4% AFR const pSurviveRebuild = Math.pow(1 - afrHourly, rebuildHrs * survivingDrives); const rebuildStress = pSurviveRebuild; // probability no new failure
// ── Step 6: Overall recovery probability ────────────────────────────────── // P(success) = structural_feasibility × (1 - P_URE) × health_factor × rebuild_stress let pSuccess = 0; if (structurallyFeasible) { pSuccess = (1 - pURE) * healthFactor * rebuildStress; pSuccess = Math.max(0, Math.min(1, pSuccess)); }
// ── Step 7: Risk classification ─────────────────────────────────────────── let riskLabel, riskColor, recommendation; if (!structurallyFeasible) { riskLabel = 'NOT FEASIBLE'; riskColor = '#c0392b'; recommendation = 'The number of failed drives exceeds ' + raidName + ''s fault tolerance (' + faultTolerance + '). Standard RAID rebuild is impossible. Consider professional data recovery services with specialised tools.'; } else if (pSuccess >= 0.85) { riskLabel = 'HIGH (Good Chance)'; riskColor = '#27ae60'; recommendation = 'Recovery is likely feasible. Proceed with a verified backup of all surviving drives before rebuilding. Monitor SMART data throughout.'; } else if (pSuccess >= 0.60) { riskLabel = 'MODERATE'; riskColor = '#f39c12'; recommendation = 'Recovery is possible but not guaranteed. Image all surviving drives first. Consider professional assistance if data is critical.'; } else if (pSuccess >= 0.30) { riskLabel = 'LOW'; riskColor = '#e67e22'; recommendation = 'Recovery is risky. High URE probability or poor drive health significantly reduces success. Professional recovery services are strongly advised.'; } else { riskLabel = 'VERY LOW'; riskColor = '#c0392b'; recommendation = 'Recovery is unlikely without professional intervention. Do not attempt DIY rebuild — further reads may overwrite recoverable sectors.'; }
// ── Step 8: Estimated recoverable data ──────────────────────────────────── const totalArrayTB = (function() { switch (raidLevel) { case 0: return totalDrives * driveSizeTB; case 1: return driveSizeTB; case 5: return (totalDrives - 1) * driveSizeTB; case 6: return (totalDrives - 2) * driveSizeTB; case 10: return (totalDrives / 2) * driveSizeTB; default: return 0; } })(); const recoverableTB = structurallyFeasible ? (totalArrayTB * pSuccess).toFixed(2) : '0.00';
// ── Format output ───────────────────────────────────────────────────────── const pSuccessPct = (pSuccess * 100).toFixed(1); const pUREPct = (pURE * 100).toFixed(2); const healthPct = (healthFactor * 100).toFixed(1); const rebuildPct = (rebuildStress * 100).toFixed(2);
resultDiv.innerHTML = '### Recovery Feasibility Results ' + '' + 'Array Configuration' + '' + raidName + ' | ' + totalDrives + ' drives | ' + driveSizeTB + ' TB each' + 'Fault Tolerance' + '' + faultTolerance + ' drive(s) max | ' + failedCount + ' failed' + 'Structural Feasibility' + '' + (structurallyFeasible ? '✅ Yes' : '❌ No — exceeds fault tolerance') + '' + 'URE Probability (rebuild)' + '' + pUREPct + '% (' + bitsToRead.toExponential(2) + ' bits read)' + 'Drive Health Factor' + '' + healthPct + '%' + 'Rebuild Survival Probability' + '' + rebuildPct + '% (' + rebuildHrs + ' hrs, ' + survivingDrives + ' surviving drives)' + 'Overall Recovery Probability' + '' + pSuccessPct + '%' + 'Estimated Recoverable Data' + '' + recoverableTB + ' TB of ' + totalArrayTB.toFixed(2) + ' TB' + 'Feasibility Rating' + '' + riskLabel + '' + '' + '' + 'Recommendation: ' + recommendation + ''; }
// Expose to global scope for onclick handlers window.raiCalculate = raiCalculate; window.raiUpdateDriveInputs = raiUpdateDriveInputs;
// Initialise on load raiUpdateDriveInputs();
})();
#### Formulas Used
1. Structural Feasibility: Feasible if failed_drives ≤ fault_tolerance RAID 0: 0 | RAID 1: N−1 | RAID 5: 1 | RAID 6: 2 | RAID 10: ⌊N/2⌋
2. URE Probability during Rebuild: P(URE) = 1 − (1 − URE_rate)bits_to_read where bits_to_read = surviving_drives × drive_size_TB × 1012 × 8
3. Drive Health Factor: H = exp( (1/n) × Σ ln(health_i / 100) ) — geometric mean of health scores
4. Rebuild Survival Probability: P(survive) = (1 − AFR/8760)rebuild_hours × surviving_drives Assumes 4% annualised failure rate (AFR) for drives under rebuild stress.
5. Overall Recovery Probability: P(success) = (1 − P_URE) × H × P(survive) [0 if structurally infeasible]
6. Recoverable Data: Recoverable_TB = Array_Capacity_TB × P(success)
#### Assumptions & References
- URE (Unrecoverable Read Error) rates sourced from manufacturer specifications: consumer HDDs ~10−14, enterprise HDDs ~10−15, SSDs ~10−16–10−17.
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