It’s always amazing to me how frequently backups silently fail. Every backup software or general common tool to back things up that I’ve seen has many points of silent failure where it just gives up copying at some point in the process or skips over files for some reason without indicating what or why.

If you don’t delete files as you go, now you have an unknown partial backup state that basically doubles your needed space.

If you delete as you go, sometimes something happens and the process stops or corrupts so your data is now split and you may have lost something.

Even trying to log all the failures during the process is amazingly difficult and solutions to work around that specific problem, themselves, somehow introduce more and new types silent failure in some type of irony.