6 ms·
One key point about retention which is not often mentioned, and indeed neither does this article, is that retention is inversely proportional to program/erase c
by userbinator 11mo ago
One key point about retention which is not often mentioned, and indeed neither does this article, is that retention is inversely proportional to program/erase cycles and decreases exponentially with increasing temperature. Hence why retention specs are usually X amount of time after Y cycles at Z temperature. Even a QLC SSD that has only been written to once, and kept in a freezer at -40, may hold data for several decades.
Manufacturers have been playing this game with DWPD/TBW numbers too --- by reducing the retention spec, they can advertise a drive as having a higher endurance with the exact same flash. But if you compare the numbers over the years, it's clear that NAND flash has gotten significantly worse; the only thing that has gone up, multiplicatively, is capacity, while endurance and rentention have both gone down by a few orders of magnitude.
For a long time, 10 years after 100K cycles was the gold standard of SLC flash.
Now we are down to several months after less than 1K cycles for QLC.
- RachelF 11mo agoEndurance going down is hardly a surprise given that the feature size has gone down too. The same goes for logic and DRAM memory. I suspect that 2035 years time, hardware from 2010 will work, while that from 2020 will be less reliable.
- Dylan16807 11mo agoAs far as I'm aware flash got a bit of a size boost when it went 3D and hasn't shrunk much since then. If you use the same number of bits per cell, I don't know if I would expect 2010 and 2020 or 2025 flash to vary much in endurance. For logic and DRAM the biggest factors are how far they're being pushed with voltage and heat, which is a thing that trends back and forth over the years. So I could see that go either way.
- lotrjohn 11mo agoCompletely anecdotal, and mostly unrelated, but my NES from 1990 is still going strong. Two PS3’s that I have owned simply broke. CRTs from 1994 and 2002 still going strong. LCD tvs from 2012 and 2022 just went kaput for no reason. Old hardware rocks.
- Dylan16807 11mo agoFor what it's worth my LCD monitor from 2010 is doing well. I think the power supplied died at one point but I already had a laptop supply to replace it with.
- dfex 11mo agoSpecifically old Japanese hardware from the 80s and 90s - this stuff is bulletproof
- jacquesm 11mo agoI still have a Marantz amp from the 80's that works like new, it hasn't even been recapped.
- userbinator 11mo agoLCD tvs from 2012 and 2022 just went kaput for no reason. Most likely bad capacitors. The https://en.wikipedia.org/wiki/Capacitor_plague https://en.wikipedia.org/wiki/Capacitor_plague may have passed, but electrolytic capacitors are still the major life-limiting component in electronics.
- londons_explore 11mo agoMLCC's look ready to take over nearly all uses of electrolytics. They still degrade with time, but in a very predictable way. That makes it possible to build a version of your design with all capacitors '50 year aged' and check it still works. Sadly no engineering firm I know does this, despite it being very cheap and easy to do.
- DoesntMatter22 11mo agoLooks like that plague stopped in 2007? I have a 8 year old LCD that died out of nowhere as well, So I'm guessing wouldn't be affected by this. Could still be a capacitor issue though
- userbinator 11mo ago
- bullen 11mo agoI concur; in my experience ALL my 24/7 drives from 2009-2013 still work today and ALL my 2014+ are dead, started dying after 5 years, last one died 9 years later. Around 10 drives in each group. All older drives are below 100GB (SLC) all never are above 200GB (MLC). I reverted back to older drives for all my machines in 2021 after scoring 30x unused X25-E on ebay. The only MLC I use today are Samsungs best industrial drives and they work sort of... but no promises. And SanDisc SD cards that if you buy the cheapest ones last a surprising amount of time. 32GB lasted 11-12 years for me. Now I mostly install 500GB-1TB ones (recently = only been running for 2-3 years) after installing some 200-400GB ones that work still after 7 years.
- Aurornis 11mo ago> in my experience ALL my 24/7 drives from 2009-2013 still work today and ALL my 2014+ are dead, As a counter anecdote, I have a lot of SSDs from the late 2010s that are still going strong, but I lost some early SSD drives to mysterious and unexpected failures (not near the wear-out level).
- bullen 11mo agoInteresting, what kind where they? Mine where all Intel.
- tensility 11mo agoOh, it would be nice if it were just feature size. Over the prior 15 years, the nand industry has doubled its logical density three times over with the trick of encoding more than one bit per physical voltage well, making the error bounds on leaking wells tighter and tighter and amplifying the bit rot impact, in number of ECC corrections consumed, per leaked voltage well.
- robotnikman 11mo agoI recently found a 1GB USB drive from around 2006 I used to use. I plugged in and most of the files were still readable! There were some that were corrupted and unreadable unfortunately.
- hxorr 11mo agoI also seem to remember reading retention is proportional to temperature at time of write. Ie, best case scenario = write data when drive is hot, and store in freezer. Would be happy if someone can confirm or deny this.
- CarVac 11mo agoI definitely remember seeing exactly this.
- userbinator 11mo agoThat's probably this: https://www.sciencedirect.com/science/article/abs/pii/S0026271418305079 https://www.sciencedirect.com/science/article/abs/pii/S00262...
- pbmonster 11mo agoI know we're talking theoretical optimums here, but: don't put your SSDs in the freezer. Water ingress because of condensation will kill your data much quicker than NAND bit rot at room temperature.
- Onavo 11mo agoWhat about magnetic tape?
- pbmonster 11mo agoFor long term storage? Sure, everybody does it. In the freezer? Better don't, for the same reason. There are ways to keep water out of frozen/re-frozen items, of course, but if you mess up you have water everywhere.
- dachris 11mo agoWould an airtight container and liberal addition of dessicants help?
- pbmonster 11mo ago
- nutjob2 11mo ago> Even a QLC SSD that has only been written to once, and kept in a freezer at -40, may hold data for several decades. So literally put your data in cold storage.
- dotancohen 11mo agoThat is literally the origin of the term.
- karczex 11mo agoThat's how it has to work. To increase capacity you have to make smaller cells where charge may easier diffuse from one cell to another. Also to make drive faster, stored charge has to be smaller, which also decrease endurance. With SLC and QLC comparison is even worse as QLC is basically clever hack to store 4 times more data in the same number physical cells - it's tradeoff.
- bullen 11mo agoYes, but that tradeoff comes with a hidden cost: complexity! I much rather have 64GB of SLC at 100K WpB than 4TB of MLC at less than 10K WpB. The spread functions that move bits around to even the writes or caches will also fail. The best compromise is of course to use both kinds for different purposes: SLC for small main OS (that will inevitably have logs and other writes) and MLC for slowly changing large data like a user database or files. The problem is now you cannot choose because the factories/machines that make SLC are all gone.
- userbinator 11mo agoThe problem is now you cannot choose because the factories/machines that make SLC are all gone. You can still get pure SLC flash in smaller sizes, or use TLC/QLC in SLC mode. I much rather have 64GB of SLC at 100K WpB than 4TB of MLC at less than 10K WpB. It's more like 1TB of SLC vs. 3TB of TLC or 4TB of QLC. All three take the same die area, but the SLC will last a few orders of magnitude longer.
- karczex 11mo agoSLC are produced, but the issue is that there is no (I'm aware of) SLC products for consumer market
- mort96 11mo agoMy problem is: I have more than 64GB of data
- londons_explore 11mo agoI'm sad that drives don't have a 'shutdown' command which writes a few extra bytes of ECC data per page into otherwise empty flash cells. It turns out that a few extra bytes can turn a 1 year endurance into a 100 year endurance.
- consp 11mo agoBlind question with no attempt to look it up: why don't filesystems do this? It won't work for most boot code but that is relatively easy to fix by plugging it in somewhere else.
- londons_explore 11mo agoThe filesystem doesn't have access to the right existing ECC data to be able to add a few bytes to do the job. It would need to store a whole extra copy. There are potentially ways a filesystem could use heirarchical ECC to just store a small percentage extra, but it would be far from theoretically optimal and rely on the fact just a few logical blocks of the drive become unreadable, and those logical blocks aren't correlated in write time (which I imagine isn't true for most ssd firmware).
- lazide 11mo agoReed Solomon codes, or forward error correction is what you’re discussing. All modern drives do it at low levels anyway. It would not be hard for a COW file system to use them, but it can easily get out of control paranoia wise. Ideally you’d need them for every bit of data, including metadata. That said, I did have a computer that randomly bit flipped when writing to storage sometimes (eventually traced it to an iffy power supply), and PAR (a type of reed solomon coding forward error correction library) worked great for getting a working backup off the machine. Every other thing I tried would end up with at least a couple bit flip errors per GB, which make it impossible.
- mrspuratic 11mo agoCD storage has an interesting take, the available sector size varies by use, i.e. audio or MPEG1 video (VideoCD) at 2352 data octets per sector (with two media level ECCs), actual data at 2048 octets per sector where the extra EDC/ECC can be exposed by reading "raw". I learned this the hard way with VideoPack's malformed VCD images, I wrote a tool to post-process the images to recreate the correct EDC/ECC per sector. Fun fact, ISO9660 stores file metadata simultaneously in big-endian and little form (AFAIR VP used to fluff that up too).
- ACCount37 11mo agoBecause no one is willing to pay for SLC. Those QLC NAND chips? Pretty much all of them have an "SLC mode", which treats each cell as 1 bit, and increases both write speeds and reliability massively. But who wants to have 4 times less capacity for the same price?
- userbinator 11mo ago4 times less capacity but 100x or more endurance or retention at the same price looks like a great deal to me. Alternatively: do you want to have 4x more capacity at 1/100th the reliability? Plenty of people would be willing to pay for SLC mode. There is an unofficial firmware hack that enables it: https://news.ycombinator.com/item?id=40405578 https://news.ycombinator.com/item?id=40405578 1TB QLC SSDs are <$100 now. If the industry was sane, we would have 1TB SLC SSDs for less than $400, or 256GB ones for <$100, and in fact SLC requires less ECC and can function with simpler (cheaper, less buggy, faster) firmware and controllers. But why won't the manufacturers let you choose? The real answer is clearly planned obsolescence. I have an old SLC USB drive which is only 512MB, but it's nearly 20 years old and some of the very first files I wrote to it are still intact (I last checked several months ago, and don't expect it's changed since then.) It has probably had a few hundred full-drive-writes over the years --- well worn-out by modern QLC/TLC standards, but barely-broken-in for SLC.
- big-and-small 11mo agoFunny enough I just managed to find this exact post and comment on google 5 minutes ago when I started wondering whatever it's actually possible to use 1/4 of capacity in SLC mode. Though what make me wonder is that some reviews of modern SSDs certainly mention that that pSCL is somewhat less than 25% of capacity, like 400GB pSLC cache for 2TB SSD: https://www.tomshardware.com/pc-components/ssds/crucial-p310-2280-ssd-review/2 https://www.tomshardware.com/pc-components/ssds/crucial-p310... So you get more like 20% of SLC capacity at least on some SSDs
- ACCount37 11mo agoThe real answer is: no one actually cares. Very few people have the technical understanding required to make such a choice. And of those, fewer people still would actually pick SLC over QLC. At the same time: a lot of people would, if facing a choice between a $50 1TB SSD and a $40 1TB SSD, pick the latter. So there's a big incentive to optimize on cost, and not a lot of incentive to optimize on anything else. This "SLC only" mode exists in the firmware for the sake of a few very specific customers with very specific needs - the few B2B customers that are actually willing to pay that fee. And they don't get the $50 1TB SSD with a settings bit flipped - they pay a lot more, and with that, they get better QC, a better grade of NAND flash chips, extended thermal envelopes, performance guarantees, etc. Most drives out there just use this "SLC" mode for caches, "hot spot" data and internal needs.
- awei 11mo agoSo AWS S3 Glacier might actually be cold
- aidenn0 11mo agoOn the other hand when capacity goes up, the cycle-count goes down for the same workload. A 4TB drive after 1K cycles has written the same amount of data as 100GB drive after 40K cycles.