Several ways of doing a complete backup. One common way is with a RAID setup, but requires two or more identical hard drives. Some RAID systems are self-healing and self-restoring, if one drive fails. Put in a new drive, and back to 100%.
Another way is with a cloning or 'migration' program, which duplicates exactly the data from the working hard drive to another of equal or larger size. But an update has to be done monthly or weekly, to stay current with program updates and changes.
Then there is the resident backup program in the OS. That can copy to another hard drive, or to an optical disk. Only problem with using a disk, it has to be re-writable, and may become more corrupt than a hard drive, with re-writes.
Another way is with a network server or NAS, which can back up several systems, and also be for additional storage.
With any form of backup or archive, longevity is a critical factor. Optical disks may not endure a good image as long as a hard drive, yet are immune to magnetic fields which can destroy data on hard drives. The solid-state drives are more secure, and possibly have a longer good retention of data.
F@H.. to solve mankind's maladies.. in our lifetimes!