Define what you are actually backing up
A 20 TB NAS does not necessarily contain 20 TB of irreplaceable data. Separate documents, project files and original media from caches, downloads and data that can be recreated. This reduces the estimate to a recovery requirement instead of the size printed on the disks.
Also separate live data from retained backup data. If files change frequently and old versions remain for months, the backup can be larger than the live dataset. Compression and deduplication can pull in the other direction. Use a measured retained-storage figure when your backup software provides one.
Build a quiet-month and restore-month budget
Suppose you have 2 TB of live data, estimate retained backups at 1.5 times that size, and enter a sample storage rate of $0.006 per GB-month. The estimate is 3,000 GB × $0.006 = $18 per month. This rate is an illustrative input; check the provider's current pricing.
Next, model a restore. At an illustrative $0.01 per GB with no applicable allowance, downloading 2,000 GB adds $20. The modeled month is $38 before requests, software, tax or any other charges. If your plan includes an applicable download allowance, the result changes. Enter that allowance explicitly rather than assuming it applies to every transfer.
Check that the product supports your source
A product described as unlimited computer backup may exclude network shares and NAS devices. Backblaze explicitly separates these uses: its Computer Backup product excludes network-mounted storage, while its B2 documentation describes NAS backup workflows. Product compatibility comes before the subscription price.
For a proposed setup, confirm that your NAS or backup application supports the destination, encryption mode and required restore method. A supported upload path alone is not proof that you can restore the data in the environment you will have after a failure.
Write down the recovery path
- Identify the replacement machine or storage where data will land.
- Keep recovery credentials and encryption keys accessible if the original NAS is unavailable.
- Restore a representative sample into a separate location.
- Verify that the files open and that the application sees a consistent state.
- Measure the transfer rate and estimate the full restore window.
The storage calculator models one month with a retained-data assumption. It does not simulate daily changes, provider-specific billing minimums or version-expiration rules. If these dominate the bill, calculate them from your actual backup history and provider contract.
Sources & scope
Reference check: 29 October 2026. Examples are our calculations, not measured provider benchmarks.