Our solution first creates a full backup. The subsequent backups are then differential backups, meaning that only changes to individual files are backed up (block-level). Every x days, a full backup is created again (basically starting from scratch, x is adjustable). This ensures that «only» the full backups are effectively as large as the source data, while the backups between the full backups consume only a fraction of the storage space they actually represent.
| Day 1 | Day 2 | Day 3 | Day 4 | Day 5 | Day 6 | Day 7 | Day 8 | … | |
| F = Full D = Differential |
F | D | D | D | D | D | D | F | D |
| Transferred (changes only) |
250GB | 5GB | 1GB | 12GB | 1GB | 2GB | 5GB | 250GB | … |
| Storage usage Total |
250GB | 260GB | 261GB | 273GB | 274GB | 276GB | 281GB | 531GB | … |
Table: Example of backup process with weekly full and daily differential backup
Despite using only 531 GB in total on day 8, all data can be restored on a daily basis. The 531GB therefore completely represents and allows restoration of 8 days of 250GB data (2000GB). The periodicity of full and differential backups can be freely chosen.