Dr. Migrate Documentation
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Understanding Backup Storage Requirements

Understanding Backup Storage Requirements

Overview

When planning your storage costs, it’s crucial to understand that backup storage is additional to your base storage requirements. Your backup retention policy determines how much extra storage you’ll need for backups.

Key Concepts

  • Base Storage: The storage needed for your active data
  • Backup Storage: Additional storage required to maintain your backup history
  • Total Storage Required = Base Storage + Backup Storage
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Dr. Migrate uses a default Backup Storage Factor of 2.5× as a conservative estimate. This can be found under: Setup → TCO Config → On-Premises Benchmark → Storage Cost

You should adjust this factor based on your actual retention policy calculations, which we’ll cover below.

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Important: More frequent backups = Higher storage requirements

The more frequently you take backups, the more storage space you’ll need. For example:

  • Taking daily backups instead of weekly backups
  • Keeping backups for longer periods
  • Having higher daily change rates

All of these increase your backup storage factor.

Part 1: Understanding Backup Storage Requirements

How Backup Frequency Affects Storage

Backup Policy Frequency Retention Typical Storage Factor
Light Weekly 30 days 1.3-1.5×
Standard Daily 30 days 1.5-1.8×
Enterprise Daily + Weekly 90 days 1.8-2.2×
Compliance Daily + Weekly + Monthly 7 years 2.2-2.5×

Example Backup Schedule

The customer has confirmed the following backup schedule:

  • Daily backups retained for 14 days
  • Weekly backups retained for 30 days
  • Monthly backups retained for 7 years (84 months)

This is an enterprise-level backup policy that requires significant storage due to its:

  • High frequency (daily backups)
  • Long retention (7 years)
  • Multiple backup types (daily, weekly, monthly)

How Incremental Backups Add Up

Each backup type contributes to your total storage requirement:

Backup Type Retention Typical Change Rate Storage Impact
Daily 14 days 2-5% changes/day ~30-70% of base
Weekly 30 days 10-15% changes/week ~40-60% of base
Monthly 84 months 25-30% changes/month ~40-50% of base

For example, with 1 TB of base storage:

Storage Type Size Explanation
Base Storage 1 TB Your active data
Daily Backups 0.5 TB 14 days × ~3.5% daily changes
Weekly Backups 0.4 TB 4 weeks × ~10% weekly changes
Monthly Backups 0.8 TB Long-term changes accumulation
Total Backup Storage 1.7 TB Additional to base storage

Total Storage Cost Example

Using Australia Southeast region pricing (AUD):

Component Size Cost at AUD $5.03/GB
Base Storage 1 TB AUD $5,030
Backup Storage 1.7 TB AUD $8,551
Total Required 2.7 TB AUD $13,581
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The example calculations in this guide use Australia Southeast pricing in AUD. Your costs will vary based on your selected region and local currency.

Part 2: Calculate Your Backup Factor

Access Azure Calculator

  1. Go to the Azure Pricing Calculator
  2. Select “Azure Backup” from the services list
  3. Choose “Configure” to start

Enter Your VM Details

Configure your workload:

  • Region: Australia Southeast (or your local region)
  • Choose “Azure VMs”
  • Set backup policy to “Standard”
  • Enter number of VMs and size per VM

Set Retention Policy

Enter your backup schedule:

  • Daily backups: 14 days
  • Weekly backups: 30 days
  • Monthly backups: 84 months (7 years)
  • Yearly backups: 0 years

Review Storage Impact

The calculator will show:

  1. Your base storage amount (per VM)
  2. Required backup storage (“Average monthly backup data”)
  3. Calculate your backup storage factor:

To determine your storage factor, divide the “Average monthly backup data” by your VM storage size:

Storage Factor = Average Monthly Backup Data ÷ VM Storage Size

For example:

  • VM Storage Size = 10 GB
  • Average Monthly Backup Data = 17.01 GB
  • Storage Factor = 17.01 ÷ 10 = 1.7×

This calculated factor is what you’ll enter in Dr. Migrate.

Part 3: Configure Dr. Migrate

Access TCO Settings

  1. Open Dr. Migrate
  2. Navigate to: Setup → TCO Config → On-Premises Benchmark
  3. Expand the “Storage Cost” section

Enter Storage Costs

Choose the appropriate SAN storage tier that matches where your backups are stored in your environment:

  • If your backups are stored on Tier 1 SAN: Enter your calculated backup factor in the “Customer Value” column of Tier 1
  • If your backups are stored on Tier 2 SAN: Enter your calculated backup factor in the “Customer Value” column of Tier 2
  • If your backups are stored on Tier 3 SAN: Enter your calculated backup factor in the “Customer Value” column of Tier 3

Enter your backup factor in the tier that matches where you actually store your backups. For example:

  • If you store backups on your Tier 2 storage, enter the backup factor in Tier 2
  • If you use dedicated backup storage (Tier 3), enter the factor there
  • Choose the tier that aligns with your storage architecture

Set Infrastructure Renewal Period

  1. Locate “The time period after which the storage infrastructure is renewed (in years)”
  2. Enter your infrastructure renewal period
  3. Typical value is 3.00 years

Verify Configuration

Check that:

  • Your calculated backup factor is entered in the “Customer Value” column of your chosen SAN storage tier
  • Infrastructure renewal period is set
  • All costs are in your local currency (AUD in this example)

Important Planning Notes

  • You must budget for BOTH base storage AND backup storage
  • Your backup storage factor (e.g., 1.7×) depends on:
    • Retention periods
    • Change rates in your data
    • Backup frequency
  • Consider these multipliers when planning capacity
  • Remember: Total Cost = (Base Storage Cost) + (Base Storage × Backup Factor × Storage Cost)
  • All costs in this guide use Australia Southeast pricing in AUD - adjust for your region