In ancient days, when folks used strange machines called typewriters, Ph.D. candidates would keep older copies of their theses in the refrigerator since if the house burned down, it would often survive (this was pre-Indiana Jones). Nowadays, a few portable SSD's (not all kept at the same location) would likely suffice (it is good to have some history, in case you overwrite something vital and don't catch it)
Another standard backup utility is Macrium Reflect, especially following Microsoft de-emphasizing its utilities (Satya wants you to use OneDrive).
But as Seamanq emphasized, you must check your backups.
Another standard backup utility is Macrium Reflect, especially following Microsoft de-emphasizing its utilities (Satya wants you to use OneDrive).
But as Seamanq emphasized, you must check your backups.