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3-2-1 backup capacity and retention planner

Size local and off-site copies, estimate retention and transfer time, and check recovery objectives in one plan.

Failure-domain separation

How to read the plan

  1. Check required capacity per backup target and across both backup targets.
  2. Confirm that the retention coverage reaches the oldest recovery point you need.
  3. Compare backup interval with RPO and full restore time with RTO.
  4. Verify actual device, site, and isolation boundaries.
Capacity limitation: This conservative model carries the entered daily change across the retention window. It does not promise deduplication or compression savings. Metadata, verification, and retry time remain outside the estimate.

RPO and RTO

RPO is the maximum acceptable data-loss window. RTO is the time allowed to complete recovery. Test local and off-site recovery paths separately.

Related checks

Use the backup and restore time planner and 3-2-1 backup guide with this estimate.

Worked examples

2 TB family library

At 20 GB changed per day, 7 daily, 4 weekly and 6 monthly points, plus 20% headroom, plan about 6.72 TB for each backup target over a 180-day window.

100 Mbps off-site path

A 2 TB first copy takes about 55.6 hours at 80% efficiency, so it misses a 12-hour RTO. Keep a separate local recovery path.

Twice-daily backup

A 12-hour interval meets a 24-hour RPO arithmetically, but failed-job alerts and the next successful run still matter.

Last reviewed: 2026-08-21