yakkoj, OK collapsing the NAS heads to the DS420 fixed a long-standing problem I had with Time Machine sparsebundle being backed up really slowly. Still not blazing fast (USB does that, even USB 3), but not a terrible stall-fest like it was on the DS712
Boy Time Machine has a mind of its own. First, there were 64MB bands, then I burnt that down and Time Machine made 2GB bands, and now this time, it settled on 256MB bands. macOS has magic 8 ball and ouija board to decide.