TIL that SSDs can lose data if left unplugged for long periods of time (only required to hold data up to 1 year), unlike HDDs which as long as the material holds it can take years.

@djlink Not only can they lose data but they can simply irrecoverably stop working if you leave them more than a year or so unplugged - dead as a doornail.

Spinny rust these days is not vastly better because the flash holding the firmware is better but not a lot better.

@djlink don't ask about post-N64 Nintendo cartridges.

@rotopenguin
(So... Switch and Switch II.)
@djlink

@djlink This claim pops up from time to time and has for a damn decade. https://www.pcworld.com/article/427602/debunked-your-ssd-wont-lose-data-if-left-unplugged-after-all.html

@RandyMongenel That article isn't debunking this claim at all though. It's debunking claims that it can happen on the scale of weeks, and explaining that you'd have to come up with a very specific scenario for that to happen. It is worth noting that a year is the minimum spec, and probably you could get 2-3 years out of them unplugged, especially if you're storing at cooler temperatures

@november @RandyMongenel The article is 10 year old, and about rather larger and more resistant technology.

Practical experience says that they decay if left unused for a long time.

@rotopenguin
Also definitely do not ask about old phones that weren't on for years, especially manufactured during a certain period, the flash chips from which die like flies. See also Wii U and the 4GB Xbox 360.
@djlink

@djlink that is a very poor-quality source; modern SSDs indeed hold data for years, and powering them also doesn't increase data retention; they're not in any technical sense related to static (which needs constant power, very little) or dynamic RAM (which needs refresh cycles every few milliseconds).
You can be pretty certain that a not end-of-write-life SSD will retain data for years to decades. If you care, some SSDs actually specify more than just a overall MTBF (often in the 10⁶ h)

@funkylab @djlink
Not powered off they don't.
An HDD can wear out with use but 25 years is easy for storage in a drawer or box in the attic. Floppy storage is far trickier.
Tape needs carefully stored.
Pressed DVDs* and especially pressed CDs are OK, but "written" ones can fade in daylight.

[* Assuming no manufacturing defects]

@raymaccarthy @djlink Ray, I'm sorry, but do you actually understand how flash memory works? powering on the SSD does exactly *nothing* to the cells until you at least read them (in which case you get a slight read wear on the cell and its neighbors), and you won't increase the charge levels inside a cell unless you erase and rewrite it, which does more damage, so the speed of charge leaking is higher than if you've just let the data alone.

(I mean, you're an EE – so model your gate capacitor!

@funkylab @djlink
There are no ideal options for SSD. That's why I have backups and the user data on my workstations and main laptop is on HDD (conventional, not shingled or helium etc). The OS is easily installed and restored from backup on a new SSD.
The point is that an unused conventional HDD will last for decades. That's unlikely for SSDs or any high capacity SD card, USB stick etc.

@raymaccarthy @djlink I honestly find the opposite to be the case - HDDs can expose mechanical degradations (air barriers, motor bearings) that tend to work against you when you leave them unpowered. But this isn't about HDDs; it's about the myth that powering on an SSD will help data retention.

@funkylab @djlink
NO, the article isn't about powering up SSDs, but they fade in a drawer.
It's proven that HDDs generally don't wear out when powered off. The bearings etc only degrade when they are spinning.
The big plus on SSDs is random access speed, not reliability, for a home user. They are not a backup medium. An SSD in an external USB box is useful for file transfer, not backups.

@djlink I'm not even sure where the myth that powering on helps data retention comes from; the last thing an SSD would want to do to increase data reliability would be doing any writing in the background.

@raymaccarthy @funkylab @djlink Neither SSDs nor HDDs are designed as reliable long-term archival/offline storage and relying on them as such is a bad idea.

They are effectively designed for dynamic/online storage.

Tapes while technically designed for offline storage are also garbage because they degrade (faster) unless dynamic conditions (such as humidity and heat) are maintained within particular ranges, so to call them truly offline/static is a lie (it's just externalizing where the dynamism happens).

The main non-vaporware digital storage I'm aware of that is somewhat acceptably static in conditions that aren't tightly controlled are variants of punched cards (particularly plasticized or metallic ones, but some paper/cardboard variants have also been found to endure surprisingly well).

(We hear of fancy glass/ceramic/whatever optical (or other) storage meant to last centuries every few years or decades but they never seem to actually materialize onto the market.)

@lispi314 @djlink @raymaccarthy @funkylab Some years ago a quaker friend was discussing options for electronic storage of their records (which they keep and readable with great care for vast times). They did indeed decide to continue to keep them on paper both because of uncertainties around digital storage media, but also because they were worried that 80 years from now someone might not have the software or information to recover some digital media type.

@raymaccarthy @djlink … the charge it holds is your bits (mutliple, because on most SSDs these days you get more than two states); the only way that loses data is by tunneling of charge through the dielectric, which follows a shot noise model. Information-theoretically, we call this a "Z-channel", because you can only get from higher to lower states, never the other way around.
Now, if left alone, a couple of these bits will actually flip – that's why there's extensive forward error correction –

@raymaccarthy @djlink and again, it's pretty likely that a not overly written to SSD does indeed retain data many years; it gets problematic only when close to write volume limits. I feel like I've explained that already.

@djlink note that yes, there's JESD218, but that specifies a lower limit (and indeed 1 a) for powered off data retention at the point in time when your SSD has reached its specified write volume; yes, electrons tunnel out of flash cells' gate capacitors, but as long as you've not written these to the end of their capacitance (erasing&rewriting makes these capacitors worse), this can all be accounted for by the SSD itself.
(the powering off is not a penalty to the SSD! Just the test condition!)

@raymaccarthy @djlink but as long as the number of these high->low state degradations is small enough, that's correctable. Flash memory is already, without long-term storage effects, a lossy medium, which you have to design your error correction for!
So, when an SSD manufacturer designs that error correction (namely, which code to use, and thus how many bits per information word to add as redundancy), they have to design it in such a way that at some erase-write cycle reliability they want to

@raymaccarthy @djlink sell to the customer. But that same redundancy that helps when cells' dielectric layers degrade due to repeated high-voltage "zapping" (right, you apply a high |E| to the cell to implant charge in flash memory!) and doesn't hold charge as well also helps with long-term storage. Just that the effect of "time and temperature", as you can imagine, is a lot smaller than the effect of "make that dielectric experience what would be called a breakdown if it was macroscopic"!
Hence

@raymaccarthy @djlink I'm really not sure where the idea that a powered SSD would be more reliable than an unpowered one – that could only be true if it would be re-writing itself in the background, which would, counter to the intent, make it wear out faster, unless the SSD is essentially unused and the re-writing was free to use arbitrary much rarely or never used pages to copy the data to. But even that would be very undesirable – who wants an SSD with a standby power usage as if written to?)

@funkylab @raymaccarthy @djlink Modern SSDs do patrol scrubbing so they do indeed rewrite bad information or marginal data when needed.
Spinny rust has btw done the same thing for many years too, some spinny rust is even smart enough to relocate data behind your back so you don't even find out about the bit of the disk that's getting dodgy for some reason.

@raymaccarthy @funkylab @djlink Hard disks also wear out if stored. However your wear is mostly component failures, oxidisation and so on so quite slow. The flash chips on the hard disk drive today will also eventually dribble their brains out and it won't work any more but the flash used is generally rather less vulnerable than the very high density flash used in an SSD.

Unlike the SSD though your HDD media is more recoverable even if the electronics is dead.

@etchedpixels @november The entire point of posting the article was that it was 10 years old. What is your basis for claiming "more resistant"?

@RandyMongenel @november larger sized gates

@djlink @funkylab High-density multi-level flash does fade over relatively short time. When powered on, the controller does periodic scrubbing of blocks that haven't been accessed recently, fixing any that have too many (correctable) errors. If left too long (a few years), errors will accumulate beyond the correctable amount and you lose data. This is not a failure of the device and is thus not reflected in MTBF figures.

Single-level flash lasts longer, typically at least 10 years.

@etchedpixels @november Are you attempting to claim that the gate size alone is an indicator of leakage rate per cell? What's the data source?

@RandyMongenel @november As I was taught the smaller the gate size the higher the gate current. The higher the gate current the higher the FN and HH stress. The higher the FN and HH stress the more leakage you get

Plus smaller flash cells contain less electrons, and multiplied by QLC etc require much less leakage before they give a wrong value. We've decreased the effective electrons per bit on high density flash by several hundred fold by a combination of multi-bit storage and density.

@djlink Well... There are minimums and there is real endurance. And real endurance depends on many things, including health. New SSD will retain data longer than SSD at end of life, for example. You'll likely get more than year in real use. But yes, it is more complex and no, SSDs are not forever.

@etchedpixels @november While technically true, it avoids the idea that gates and cells can be constructed in a way to offset those limitations.

@RandyMongenel @november I am not up to date on the latest state of things but other than oxide thinning there wasn't a lot going on to improve that side of things.
And it was only seen as mattering for stuff like firmware (which for most devices is in 1 cell per bit flash anyway). SSDs so long as they get powered on now and then do all the needed scrubbing.

It's important to remember "1 year high temp" isn't "all fails a day later" it's almost every unit lasts way longer.