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.

Kevin Granade

@djlink I mean yea, but both are not ok for archiving, you actually want them in a live enclosure, preffereably with redundancy

sodiboo :pride_heart:

@djlink@mastodon.gamedev.place

Dave Rahardja

@djlink IMO the only material proven to hold digital data for decades at this point is tape, as evidenced by the tape reels they keep finding in storage warehouses whose contents are successfully read back https://www.tomshardware.com/software/linux/recovered-unix-v4-tape-quickly-yields-a-usable-operating-system-nostalgia-addicts-can-now-boot-up-unix-v4-in-a-browser-window

I suppose HDDs can hold archival data, but there are way more ways for spinning discs to fail than tape when stored for long periods of time. But maybe we can use magnetic microscopy to recover their data even if their circuits have died, their motors have failed, or their lubricants have died out. https://garnerproducts.com/hubfs/ucsd_recovery_of_partially_degaussed-hdds.pdf

Bob Tregilus

@djlink Interesting. I use HDDs for my backups. Sounds like I should continue to do so.

Marcus Müller

@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)

David Amador

@drahardja they don’t make tech as they used to xD

Marcus Müller

@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.

Dave Rahardja

@djlink Heh heh, I know you’re joking, but I think the engineering balance has shifted. We want faster access, higher data density, smaller sizes, and fewer moving parts. Data longevity beyond 1–3 years of non-use is not even a selling factor any more.

kimchitea

@djlink thank you for the reminder to plug in my backup drive

doctorwu2357

@djlink i grew up thinking that the data stored in drives was permanent, but then quickly learned about the unfortunate reality of entropy

Marcus Müller

@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!)

mossman

@drahardja @djlink tape storage has its own risks due to the fact it's exposed to the elements. I've heard of cases where audio tape gets mouldy, flaky, sticky, magnetised / demagnetised, disintegrates, unrolls, crinkles, etc.

Dave Rahardja

@mossman @djlink Oh for sure. But given *the same storage conditions* I’ll put my money on tape lasting longer than HDD, SDD, or optical drives.

mossman

@drahardja @djlink I'd imagine you'd need more controlled conditions for tape than the others - they probably don't care so much about temperature, humidity and magnetism. Memory is basically impervious to everything except time and electricity.

Ray McCarthy

@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]

Ray McCarthy

@digitalstefan @djlink
The highest capacity CF car I have is 1G Byte. It's about x3 the area of the 512G Byte SSD. So the cells could be over 2000x bigger. Likely to be more stable.

I have a 1T micro SD Card in an ex-Chromebook running Linux Mint (64K Flash drive). I don't expect much life from it even powered mostly daily, but the contents are on my server, 2x workstations and a "real" laptop. The 2x workstations and laptop each have SSD and an HDD for user data.

Nobody ناچیز नास्ति (he/him)

@djlink what about SD cards?

Ray McCarthy

@mossman @drahardja @djlink
Magneto-0ptical is the best easily re-writable for stability but due to lack of capacity went out of fashion by the late 1990s. I think about 256M for 3.5". I presume minidiscs are the same stuff, so likely to outlast "mix" cassette tapes and MP3s on SD cards.

Marcus Müller

@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!

Marcus Müller

@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 –