I am running Norton 360 Premier on Windows 10. I have a 500 Gig OS drive (on SSD) and a 1 TB data drive on HDD.
My OS drive contains 200 GB, the data drive 700 GB. I also have a separate drive for backup, a 1 TB.
I only backup photos, music and financial files, which take up about 100 GB.
Norton 360 is set to conduct automatic, incremental backup. For the second time in less that a year it has created a backup file that totally uses the backup drive (1 TB). Last time, I had to wipe the backup and start again. It has done the same thing again in about five months.