Overview
Backup capacity is not simply production data multiplied by the number of restore points. The result depends on full and incremental architecture, synthetic fulls, forever-incremental chains, compression, deduplication and retention processing.
Engineering considerations
A useful first model starts with production data, estimates the daily change volume, then applies the intended daily, weekly and monthly restore-point policy. Treat the resulting figure as a planning estimate until the backup product's actual storage model is known.
How to plan it
Keep capacity for operational growth and temporary retention-processing needs. Also consider immutability, replication and off-site copies separately: resilience and ransomware recovery can require additional storage beyond the primary repository.
Design implications
Test restore operations. A repository that is large enough but cannot deliver the required restore throughput is not necessarily meeting the recovery requirement.
Operational considerations
The Backup Storage Calculator deliberately labels its model as approximate because backup products implement retention differently.