FullSync
As a backup solution, I've always preferred a simple mirror of files and directories rather than incrmental / compressed / archives that need to be restored by a proprietary program. I used to hack out my own batch scripts and that always worked well, but a hassle to maintain, update and test.
Until recently, I was using
SyncToy, which is free, but FullSync is just another example of a FOSS program that is simply better, in almost every way, than what Microsoft offers.