Support multi-stage storage for backups

To be secure, backups must be performed to a location other than the original disk. However, it is not always practical to connect an external hard disk or a network. However, most recent PCs offer a card reader (SD or other).

I would like to able to define my card reader as the primary backup location, with my external hard disk as secondary. Continuous backups could be performed to the memory card (primary location), and then migrated to the hard disk (secondary) when it becomes available.