That's incorrect. RAID is a system build on top of hard drives for redundancy. Redundancy (for this use of the word) is simply duplication across multiple hard-drives, which doesn't require a system at all.

Really, this is a very simplistic view of long term storage.

A RAID is not magically more reliable than a single drive, it needs a bunch of infrastructure and it needs to be duplicated to some other location far away enough to ensure that a single catastrophe such as a fire does not destroy your entire raid.

You are missing the wood for the trees: hard drives and raid devices are storage mechanisms that fall far short of the boundary conditions set to keep something permanently, at worst you will store your data for a couple of hour like that and in ideal conditions maybe for a couple of years, but on a scale of decades or centuries they are useless as a complete solution, though they could be part of such a solution.

I wonder how terrifying it would be to get a notification every time a single underlying storage device on something like Dropbox or S3 failed. We all know there is some kind of redundant system but how often does your data get moved around because of failures?

At that scale it's probably like a slow rain.

You could be made to feel better if the alert only came when it concerned your data. But even then, and going by the NAS sitting under my desk you could be months without any activity and then suddenly two drives fail in two weeks. It's a nice little random data generator.

Ah yeah I was unclear there, I meant notifications of the devices under your own data.

e: Also, is it so surprising that your drives failed around the same time? It’s likely they were purchased together!

Past a certain point it would be just a part of the job. As long as you have hot spares, you'd just go around replacing failed drives every day or whenever.

Just saying to yourself "I save all my stuff on two drives" is a system. It's just kind of a crappy one that's really prone to failure.