My laptop has a folder with all my writing, except already published material. An external drive has all my writing including already published material. A USB drive has all my writing including already published material. The laptop's hard drive and the external drive are backed up daily to a third external hard drive. The laptop's hard drive is also periodically backed up to a different external hard drive. Another set of external hard drives also have full copies of all my writing including already published material. I also periodically backup items to a hard drive that is kept in a water-proof, fireproof safe. And, because I've made a habit in recent years of saving every file and every revision, the folder with all my writing is over 10GB in size with over 5,000 files. Overkill, maybe, but if you've ever lost anything, it's well worth the relative peace of mind.
Also, in the unlikely event I should ever become famous, future English archaeologists or whoever will be able to see the progress of things I've written and what I changed when and all that stuff that will be of great interest to like a half dozen people in the world, or precisely zero if I never become famous which is the more likely case.