Mirroring the entire drive, occasionally, is a good idea.  Doing that when only a few hundred files have changed in a month, on the other hand, can eat a lot of time and computing power.

I don't want Gates Of Hell's crew managing my files.  They seem intent on ticking me off every chance they get. Their email program is like something a beginner coder would write.  Their general system is better described as bloatware. At least the got their heads PART way out of the sand and its said restoring a system doesn't take it back to its original state - empty.

A RAID system is way overkill for me. I'm just updating a mirror image on two home-hobby computers, and updating photo and data from two people. 

On tape/serial drives - Ha!  I think I came across one of my old tape cartridges from back in the days, a week or so ago, while cleaning part of the shop.  

I so looked forward to leaving that tape behind for a disk drive, though it wasn't as bad as the serial drive I used on my TI-99 headed toward fifty years ago.  Still, even that trumped the met tapes I used when I worked for the feds, as a repairman for the, at the time, most portable computer in the world [around 300# and with its whopping 180 k of memory].

Knock on wood. I've had about fifteen hard drives and the only one that ever failed was on my sister-in-laws old computer.  I've even had several that lived 15 years.

My good luck may be, as others noted, because Murphy didn't feel it worth his time to visit a computer with two drives [and a click and drag apart].

I suspect it'll only be a matter of time before someone puts out units with permanent optical disks, since, mechanics aside, they information will store indefinitely and, since they only have to fire up for backups, there's little wear and tear on their mechanical portions.