rdiff with keep of 1 deletes all data then syncs all data
We had a problem with one of our systems and generating masses of data changes each day, so we changed our retention (keep) from 12 to 1, thinking backupninja will just sync the changes. What seems to happen is the retention cleanup runs first, removing all data, then runs the rdiff-backup and syncs all the data again. This is obviously taking much more time and IO.