Hydration is the term onedrive uses to represent how its files that are cloud only will still have local placeholders, and when winapi requests them, it will download and “hydrate” the file.
I am looking for any backup software that has this behaviour, except rather than pointing to microsoft’s servers for the backup, I can point to any folder or partition or external hard drive as the backup location.
Windows seems to give a sample app for this https://learn.microsoft.com/en-us/windows/win32/cfApi/build-a-cloud-file-sync-engine
