A five hundred gigabyte external drive costs about a hundred dollars, which means the storage problem in backup is finished. The backup problem is not, because backup was never a storage problem.
It is a problem about human beings, and it has two parts that get consistently confused with each other.
The first is that anything requiring you to remember will not happen. A drive on the desk that you plug in and copy files to on Sundays works for about three weeks. Then a Sunday gets missed, and another, and eight months later there is a drive containing an accurate picture of a computer as it was last autumn. Everyone who has done this believes they have a backup right up until the moment they check the date on it.
The automatic systems now appearing in operating systems fix this properly. You attach a drive, agree once, and it runs without further involvement. That is the correct design, and it is a real improvement over anything that came before.
It does nothing about the second part, which is location.
The drive is sitting eighteen inches from the machine it protects. Consider what actually destroys people’s data. Fire takes the room. Theft takes the bag and everything near it, and a small external drive next to a laptop is exactly what a burglar picks up. A flood, a burst pipe, a surge through the mains, all of them reach both objects, because both objects are in the same place.
A copy in the same room as the original protects against precisely one failure, which is the disk inside the computer dying on its own. That is a common failure and worth defending against. It is not the one that produces the phone calls where somebody has lost fifteen years of photographs.
Which is why the online services now starting up interest me despite being slow and awkward. They get the location right, and location is the part nobody solves with a purchase. The obstacle is the upstream capacity on a domestic line, where the first copy of a large collection takes days, and there is no way around that until the connections change.
In the meantime the honest advice is unglamorous. Buy two drives, keep one automatic and attached, and keep the other at your office or your parents’ house, and swap them occasionally. Nobody will do this. It remains correct.