This: https://github.com/AmesCornish/buttersink
seems a good fit for Rockstor. Integrating would add encryption and failure recovery among other features. It’s written in Python like Rockstor. A simple test would be to pass Rockstor snapshot paths as buttersink source & destination parameters with the destination being in form: ssh://user@host/path, and buttersink would then do the rest. Something to consider?