Why I'm usually unnerved when modern SSDs die on us

What is so frustrating about SSDs is how very poorly they compare to previous incarnations of solid state storage.

Using Disk-On-Chip and/or IDE-pin-compatible CF cards, I had many, many devices in the field that lasted, mounted read-only, for decades An entire sect of the computing industry came to rely on these parts as alternatives to spinning media that could not mechanically fail.

This is not the case with SSDs at all. They fail left and right, even mounted read-only, for all manner of complicated and interesting reasons. It's very frustrating that SSDs are not a step forward in reliability from spinning media and are a step downward compared to (for instance) a 16MB consumer CF card from Sandisk, circa 2000.

rsync.net filers, which need a boot mirror, are always constructed with two unrelated SSDs - usually one Intel part and one Samsung part - so that when the inevitable usage-related failure occurs, it does not occur simultaneously to both members of the mirror which have, being a mirror, been subjected to identical usage-lives.[1]

We shouldn't have to do that.

[1] I can't overstate this - if you need a RAID mirror, do not use identical SSDs for the two members of the mirror. There are many, many cases of SSDs failing not due to "wear" or end-of-life, but due to weird usage edge cases that cause them to puke ... and in a mirror, you give the two parts identical usage ... we either get two different generations of Intel part (current gen and just-previous gen) or we get current Intel and current Samsung ...

Complete aside, the fly-height of a magnetic head is actually fractions of a nanometer (i.e. hundreds of picometers).

EDIT: I got this from a talk by Bryan Cantrill[1]. The fly-height is allegedly 0.8 nanometers (800 picometers).

[1]: https://youtu.be/fE2KDzZaxvE?t=1551

In a mechanical hard drive, there are moving parts which can wear out due to friction, etc.

SSDs are solid-state, so it seems like at least theoretically, it should be possible to build one that keeps working for decades. e.g. I have solid-state hardware from the 70s and 80s which still functions.

I've always been a little mystified as to why SSDs' data areas wear out for that reason,[1] but that's a whole separate issue. The author of the article is writing about sudden failure of the device as a whole.

There are only two explanations I've ever heard for short lifetimes in electronics as a general industry.[2]

For devices manufactured after about 2000 there's tin whiskers,[3] which began to be a problem because of RoHS requirements. I'm not sure if that applies here, though.

If the device includes electrolytic capacitors, my understanding is that those generally have a finite lifetime as well, and it can be fairly short if they're poorly-made.

I'm not a hardware expert, though, so I'd be interested in hearing about other factors, and I'm sure the author of the article would too.

[1] I've seen lots of writeups of how wear-leveling works, etc., but never a good physical explanation of what is actually wearing out over time.

[2] Obviously there are other factors for specific devices, or specific designs. E.g. maybe parts of a specific device break over time due to thermal expansion and contraction if the device wasn't engineered to handle that properly.

[3] https://nepp.nasa.gov/whisker/background/