Backup Retention & Storage Growth Estimator

ANA›Life Services Authority›National Calculator Authority›Backup Retention & Storage Growth Estimator

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Backup Retention & Storage Growth Estimator

Calculate total backup storage needed based on your data size, daily change rate, retention period, backup frequency, and compression/deduplication ratios.

Total Data Size to Back Up (GB)

The full size of the dataset for the initial full backup.

Daily Change Rate (%)

Percentage of data that changes each day (typical: 2–10%).

Retention Period (Days)

How many days of backups to retain.

Full Backup Frequency (Days)

How often a full backup is taken (e.g. every 7 days = weekly).

Compression Ratio

Ratio of original to compressed size (e.g. 1.5 means 33% reduction). Use 1 for no compression.

Deduplication Ratio

Ratio of logical to deduplicated size (e.g. 2.0 means 50% reduction). Use 1 for no dedup.

Annual Data Growth Rate (%)

Expected annual growth of your primary data set.

Forecast Period (Years)

Number of years to project storage requirements.

Calculate

### Results

Full Backup Size (after compression & dedup) Incremental Backup Size per Day (after compression & dedup) Number of Full Backups in Retention Window Number of Incremental Backups in Retention Window Total Backup Storage Required Today**** Recommended Storage (with 20% overhead)

#### Storage Growth Forecast

YearPrimary Data (GB)Total Backup Storage (GB)With 20% Overhead (GB)

function bacCalc() { const errEl = document.getElementById('bac-error'); errEl.style.display = 'none'; errEl.textContent = '';

const dataSize = parseFloat(document.getElementById('bac-data-size').value); const dailyChange = parseFloat(document.getElementById('bac-daily-change').value); const retention = parseInt(document.getElementById('bac-retention').value); const fullFreq = parseInt(document.getElementById('bac-full-freq').value); const compression = parseFloat(document.getElementById('bac-compression').value); const dedup = parseFloat(document.getElementById('bac-dedup').value); const growthRate = parseFloat(document.getElementById('bac-growth').value); const years = parseInt(document.getElementById('bac-years').value);

// --- Validation --- const errors = []; if (isNaN(dataSize) || dataSize 100) errors.push("Daily Change Rate must be between 0.1% and 100%."); if (isNaN(retention) || retention = 1."); if (isNaN(dedup) || dedup = 1."); if (isNaN(growthRate) || growthRate = 0."); if (isNaN(years) || years 20) errors.push("Forecast Period must be between 1 and 20 years."); if (!isNaN(fullFreq) && !isNaN(retention) && fullFreq > retention) errors.push("Full Backup Frequency cannot exceed the Retention Period.");

if (errors.length > 0) { errEl.innerHTML = errors.join(''); errEl.style.display = 'block'; document.getElementById('bac-result').style.display = 'none'; return; }

// --- Core Formulas --- // Effective reduction factor = compression * dedup const reductionFactor = compression * dedup;

// Full backup size after compression & dedup // fullBackupSize = dataSize / reductionFactor const fullBackupSize = dataSize / reductionFactor;

// Incremental backup size per day after compression & dedup // incrementalSize = dataSize * (dailyChange / 100) / reductionFactor const incrementalSize = (dataSize * (dailyChange / 100)) / reductionFactor;

// Number of full backups within retention window // nFull = floor(retention / fullFreq) + 1 (the +1 accounts for the most recent full backup) const nFull = Math.floor(retention / fullFreq) + 1;

// Number of incremental backups within retention window // Each full backup cycle has (fullFreq - 1) incremental days // nIncremental = retention - nFull (days not covered by a full backup) // Simplified: total days in retention minus the days that are full backup days const nIncremental = retention - Math.min(nFull, retention);

// Total backup storage today // totalStorage = (nFull * fullBackupSize) + (nIncremental * incrementalSize) const totalStorage = (nFull * fullBackupSize) + (nIncremental * incrementalSize);

// Recommended storage with 20% overhead buffer const recommended = totalStorage * 1.20;

// --- Forecast --- // For each year y (1..years): // projectedDataSize(y) = dataSize * (1 + growthRate/100)^y // projectedTotal(y) = (nFull * projectedDataSize(y) / reductionFactor) // + (nIncremental * projectedDataSize(y) * (dailyChange/100) / reductionFactor) // = projectedDataSize(y) / reductionFactor * (nFull + nIncremental * dailyChange/100)

const storageMultiplier = (nFull + nIncremental * (dailyChange / 100)) / reductionFactor;

function fmt(val) { if (val >= 1024 * 1024) return (val / (1024 * 1024)).toFixed(2) + ' PB'; if (val >= 1024) return (val / 1024).toFixed(2) + ' TB'; return val.toFixed(2) + ' GB'; }

// --- Populate Results --- document.getElementById('bac-r-full').textContent = fmt(fullBackupSize); document.getElementById('bac-r-incr').textContent = fmt(incrementalSize); document.getElementById('bac-r-nfull').textContent = nFull; document.getElementById('bac-r-nincr').textContent = nIncremental; document.getElementById('bac-r-total').innerHTML = '' + fmt(totalStorage) + ''; document.getElementById('bac-r-recommended').textContent = fmt(recommended);

// Forecast table const tbody = document.getElementById('bac-forecast-body'); tbody.innerHTML = ''; // Year 0 = current const row0 = document.createElement('tr'); row0.innerHTML = Now${dataSize.toFixed(2)}${totalStorage.toFixed(2)}${recommended.toFixed(2)}; tbody.appendChild(row0);

for (let y = 1; y Year ${y}${projData.toFixed(2)}${projStorage.toFixed(2)}${projRec.toFixed(2)}`; tbody.appendChild(row); }

document.getElementById('bac-result').style.display = 'block'; }

#### Formulas Used

Effective Reduction Factor: reductionFactor = compressionRatio × dedupRatio

Full Backup Size (compressed & deduped): fullBackupSize = dataSize / reductionFactor

Incremental Backup Size per Day (compressed & deduped): incrementalSize = dataSize × (dailyChangeRate / 100) / reductionFactor

Number of Full Backups in Retention Window: nFull = floor(retentionDays / fullBackupFrequencyDays) + 1

Number of Incremental Backups in Retention Window: nIncremental = retentionDays − nFull

Total Backup Storage Required: totalStorage = (nFull × fullBackupSize) + (nIncremental × incrementalSize)

Recommended Storage (with 20% overhead): recommended = totalStorage × 1.20

Year-Y Projected Primary Data: projectedData(Y) = dataSize × (1 + annualGrowthRate / 100)Y

Year-Y Projected Backup Storage: projectedStorage(Y) = projectedData(Y) × (nFull + nIncremental × dailyChangeRate / 100) / reductionFactor

#### Assumptions & References

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References

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