3-2-1 backup sizing: offsite copies for 3TB data on $200/month budget

Part of our guide on designing fast restore backup plans

Consolidated 3-2-1 rule and scope assumptions

3-2-1 backup rule summarized: keep three total copies of your data, store those copies on at least two different media types (for example internal disk and cloud), and keep at least one copy offsite to protect against local disasters. This single consolidated explanation replaces repetitive restatements elsewhere.

Budget scope assumptions for the rest of this article (explicit — please confirm for your case): the specified $200/month is treated primarily as the recurring monthly budget for offsite (cloud) storage and associated recurring cloud costs (storage fees, egress fees, API/transaction fees). It does not include one-time hardware purchases for local backups (external drives, NAS), nor does it automatically include one-time appliance costs. If you want those amortized into a monthly budget, state that explicitly and rerun the calculation.

We also assume the baseline dataset size is 3 TB of effective stored data after any primary compression. We will show how data-change rates, incremental backup frequency, deduplication, and compression alter recurring usage and costs.

Provider pricing examples and sources (verify current rates)

Below are representative published pricing examples as of the time of this writing. Prices change, so treat these as concrete examples and follow the provided links to verify current pricing for your account and region. If that sounds like your situation, read up on backup sizing on fixed budget next.

Backblaze B2: storage $0.005/GB-month (≈ $5/TB-month), download (egress) $0.01/GB (≈ $10/TB) for many use cases; source: Backblaze B2 pricing page (https://www.backblaze.com/b2/cloud-storage-pricing.html).

Wasabi (hot cloud storage): flat storage ~$5.99/TB-month in some plans (varies by region/promotions), with no egress fees on some plans — check current terms; source: Wasabi pricing (https://wasabi.com/pricing/).

AWS S3 (Standard): storage ~ $23/TB-month in US East for S3 Standard (pricing varies by region), with egress (data transfer out) typically starting at $0.09/GB (~$90/TB) for the first tens of TBs (see S3 Data Transfer Out); source: AWS S3 pricing (https://aws.amazon.com/s3/pricing/).

Google Cloud Storage (Standard): storage ~ $20-$24/TB-month in many regions, with egress charges that vary by destination; source: Google Cloud Storage pricing (https://cloud.google.com/storage/pricing).

Microsoft Azure Blob Storage (Hot): storage ~ $20-$25/TB-month; egress rates vary by region and tier; source: Azure Storage pricing (https://azure.microsoft.com/en-us/pricing/details/storage/blobs/).

Notes on these examples: Backblaze and Wasabi are commonly used for cost-efficient backups and illustrate how low-cost providers or particular plans can change the affordability of additional offsite copies. Major cloud providers (AWS/GCP/Azure) usually cost more per TB and add non-trivial egress costs.

Explicit cost formula and how to calculate number of offsite copies

Use this simple formula to estimate monthly recurring cloud cost for N full copies (no dedupe/compression): MonthlyCost = N * DataSize_TB * PricePerTB_Month + MonthlyEgressEstimate + MonthlyAPIFees.

DataSize_TB is the size of one full backup (3 TB in your case). PricePerTB_Month is the published storage cost per TB-month for the tier you choose. MonthlyEgressEstimate is an expected monthly outgoing data transfer cost (e.g., occasional restores or data pulls). MonthlyAPIFees are small for many providers but can matter for high transaction counts.

Solve for N (number of full offsite copies you can afford given budget B): N_max = floor((B – MonthlyEgressEstimate – MonthlyAPIFees) / (DataSize_TB * PricePerTB_Month)). This gives the number of full cloud copies within the recurring budget. If you plan to amortize hardware or want to include other recurring costs in B (such as managed backup software licensing), subtract those first.

Example variables you must decide or estimate for your scenario: PricePerTB_Month (choose a provider), expected MonthlyEgressEstimate (based on how often you restore full/partial data), MonthlyAPIFees (from provider), and whether deduplication/compression will reduce effective stored size.

Detailed cost calculation examples using the formula

We show three concrete examples using published provider rates to illustrate how many full offsite copies fit into $200/month. All egress estimates are conservative examples — actual egress depends on your restore frequency and data transfer patterns. Egress estimates here are labeled as estimates and linked to provider pages for verification.

Example A — Backblaze B2 (low-cost): Storage $5/TB-month, modest egress $10/TB-month estimate. Compute N_max: MonthlyStoragePerCopy = 3 TB * $5/TB = $15. Subtract estimate of egress/API: assume $10 (one small restore or monthly overhead). Budget for storage = $200 – $10 = $190. N_max = floor(190 / 15) = floor(12.66) = 12. Practically: Backblaze pricing makes many copies affordable on paper, but remember Backblaze B2 charges for object downloads and can charge transaction fees — check current terms: https://www.backblaze.com/b2/cloud-storage-pricing.html.

Interpretation A: If you truly store full copies without extra per-transaction or lifecycle constraints, Backblaze-level storage pricing could allow multiple full copies. In reality, backup software and access patterns, retention rules, and transaction costs typically reduce that theoretical maximum.

Example B — Wasabi (example promotional): Storage $6/TB-month, egress variable or sometimes included depending on plan. MonthlyStoragePerCopy = 3 TB * $6 = $18. If egress is $0 (plan includes it), N_max = floor(200 / 18) = 11. Practical note: Wasabi's pricing terms or region may require minimums; verify at https://wasabi.com/pricing/.

Example C — AWS S3 Standard: Storage $23/TB-month, egress say $50/TB monthly expected for occasional restores. MonthlyStoragePerCopy = 3 TB * $23 = $69. Subtract egress estimate $50: budget for storage = $150. N_max = floor(150 / 69) = floor(2.17) = 2 full copies. But be careful: AWS also applies per-request charges and higher egress for larger restores; consult https://aws.amazon.com/s3/pricing/.

Interpretation C: With mainstream providers at $20–$25/TB-month, you can sometimes afford two full copies within $200 if egress is limited, but often only one full copy is the safe assumption when you include realistic egress and API fees.

How change rate, incremental backups, deduplication, and storage tiers affect affordability

Full copies are the most expensive recurring model. In practice, backups use one initial full backup and then incremental or block-level changes. This reduces monthly storage growth and egress because only changed blocks are uploaded and retained as incremental deltas.

Effective stored size depends on your change rate (delta per month). Example: if your 3 TB dataset changes by 10% monthly and you retain 3 monthly snapshots, naive storage without dedupe could require roughly 3 TB (base) + 0.3 + 0.3 = 3.6 TB depending on how snapshots are implemented. Many backup systems use chunk-level dedupe so multiple snapshots multiply the effective stored size far less.

Deduplication/compression example: if your backup software achieves 30% reduction on average, your effective 3 TB becomes 2.1 TB. Use that reduced size in the cost formula: MonthlyStoragePerCopy = DataSizeEffective_TB * PricePerTB. This can make a second offsite copy feasible.

Tiering: cold/archival tiers (e.g., AWS Glacier, Google Archive, Backblaze Archive options) can reduce storage cost to single-digit $/TB-month but impose retrieval delays and possible retrieval costs. Use cold storage for long-retention secondary copies and hot storage for the primary offsite copy.

Practical recommendations and an actionable plan for $200/month

1) Default safe plan (recommended for most small businesses): one full cloud copy of 3 TB in a trusted provider (pick based on feature needs and pricing) + one local copy on external HDD/NAS. Use incremental backups after the initial full upload to limit monthly transfer and storage growth. Budget: choose a cloud provider where 3 TB fits comfortably under $200 after accounting for modest egress (e.g., AWS S3, Google Cloud, Backblaze, Wasabi — verify current pricing).

2) If you want two offsite copies within $200: target a low-cost provider or mix hot + cold tiers, and rely on deduplication. Steps: measure dedupe ratio and change rate, then apply the formula N_max = floor((B – Egress – API) / (Data_TB_effective * $/TB)). If that yields N>=2, proceed; otherwise keep one cloud + local.

3) To minimize recurring costs while preserving resilience: keep one hot (frequently accessed) cloud copy and a second archival copy in a cold tier (cheaper storage, slower restores). This often gives the practical resilience of two offsite copies without paying hot-tier prices for both.

4) Always budget expected egress for at least one restore per year and for testing restores quarterly. Include that egress estimate in your monthly budgeting (e.g., estimate annual expected egress then divide by 12).

5) Test restore procedures periodically and verify that snapshots and retention policies actually meet your RTO/RPO objectives.

1. Decide whether $200/month covers only recurring cloud costs or also amortized hardware and software (clarify your budget scope).
2. Measure current change rate (percentage of data modified per month) and test dedupe/compression on a sample.
3. Pick 2–3 provider options from the examples and check region-specific rates and terms (storage, egress, transactions).
4. Apply the N_max formula to each provider using your effective data size and egress estimate.
5. Implement: local copy on external HDD/NAS + cloud offsite copy (hot or hot+cold hybrid depending on budget).
6. Schedule periodic restore tests and review costs quarterly.

Risks of skimping and final summary

If you reduce offsite copies below the 3-2-1 minimum of one offsite copy, you are exposed to catastrophic local events. If you meet the minimum but cannot afford a second offsite copy, mitigate risk with robust testing, offsite encryption, and a cold-tier second copy if possible.

Summary: With realistic provider pricing and egress included, $200/month reliably funds one full 3 TB offsite cloud copy plus local backups. Two full hot-tier offsite copies are often only achievable with low-cost providers or data reduction techniques (dedupe/compression) or by using cold storage for the second copy. Use the provided formula and the cited provider pages to calculate your exact N_max for your chosen provider and assumptions.

Questions people still ask

I manage backups for small businesses and used published provider pricing pages to construct realistic examples. Always verify current rates for your region and test restores.