The short version, from Veeam’s v13 user guide (checked October 16, 2026):
- Bucket: Object Lock and versioning on, no default retention and no lifecycle rules. Most S3 platforms only let you turn Object Lock on when the bucket is created, and Veeam says not to change either setting after you add the bucket.
- Repository: add an S3-compatible object storage repository with our endpoint and your access keys, and turn on immutability in the wizard.
- Immutability period: 1 to 999 days. Veeam adds a block generation period on top, 10 days for S3-compatible storage, so a 30-day setting can keep backups locked for up to 40 days.
- Jobs: point a backup job or backup copy job at it, or add it to a scale-out backup repository as the performance or capacity tier.
Plan capacity for the lock, not only the retention. Locked versions can’t be removed early, so the space you use follows your immutability period plus the block generation days.