You define a backup policy and attach it to any volume, at creation time through the storage class or at any point later.
What happens in the background:
Snapshot first, then backed up into S3
Only the delta since the last backup
Merging deltas into larger deltas or full versions
You can restore the backup into any cluster that you want: a new PVC based on a specific timestamp or a generation.
See how it works: https://www.simplyblock.io
Chapters 0:00 Backup and restore
0:22 Backup policies
2:44 Restore into any cluster
3:46 Snapshot consistency groups