Yeah the process is to run a full backup weekly, and keep four weeks of backups. This mimics the old rsnapshot system, but sends the data directly to S3. In this particular case, the total amount of data is only less than 50GB, so the cost of a weekly backup is not great. The goal was to eliminate the dedicated backup server which ran pull backups via rsync/rsnapshot. Having each host back itself up to S3 directly is cheaper than paying for a backup host (including the time spent maintaining the backup host itself). As far as I understand, borgbackup requires a dedicated backup server.