5 ms·

Interestingly, unpowered flash memory has much higher retention rates at low temperatures and much SHORTER retention rates at elevated temperatures (the typical

Interestingly, unpowered flash memory has much higher retention rates at low temperatures and much SHORTER retention rates at elevated temperatures (the typical JEDEC spec is just 1 year retention at 30C unpowered). Flash memory in a freezer (assuming you don't have cold-induced circuit board failures due to CTE mismatch) could last hundreds of years. In a hot car, maybe a month. https://www.curtisswrightds.com/media-center/blog/extended-temperatures-flash-memory https://www.curtisswrightds.com/media-center/blog/extended-t... None of that is particularly surprising, but what's interesting is that write endurance can have the opposite effect... Writing at high temperature (followed by cooling to ambient... or lower) actually improves data retention over just writing at ambient.

userbinator 4y ago
Is the 1-year spec after all the rated program/erase cycles have already been used, so the flash cells are worn and much "leakier"? That's still rather disturbing, since I have datasheets for NAND flash from around 2 decades ago that specify 10 years retention after 100K cycles (although probably at 25C), and some slightly newer ones with 5 years / 1.5K cycles (MLC); and also explains the increasing secrecy surrounding the flash industry. The very few I could find for TLC don't even mention retention and endurance is vaguely specified, and refer you to some, probably super-secret, qualification report for the actual numbers. Then again, perhaps I shouldn't be surprised ever since they came up with the misnomers that are "TLC" and now "QLC", and nearly drove SLC to extinction. I don't want 3x or 4x more storage for the same price (or 1/3 or 1/4 the price) if it's 1/8th or 1/16th exponentially more unreliable --- that's how the physics works and there's no way around that --- but that's what they seem to be pushing for. You can get $13 128GB TLC SSDs as mentioned in the article but I don't see any $39 128GB SLC SSDs being made, nor $13 ~40GB SLC SSDs, despite the fact that such a device would have the exact same cost per NAND cell (and as a bonus, be much faster and simpler since SLC needs much less ECC and advanced wear leveling algorithms than TLC/QLC.)
- smartbit 4y ago
  > but I don't see any $39 128GB SLC SSDs being made, nor $13 ~40GB SLC SSDs Shouldn’t it be 2^3 times more expensive than TLC? IOW a $104 128GB SLC SSD or a $13 16GB SLC SSD. Edit: guess you’re right userbinator
  - userbinator 4y ago
    No. Each cell in TLC stores three bits (and has 8 actual voltage levels, hence the misnomer), and thus TLC should either be a third of the cost of SLC at the same density, or three times the density as SLC for the same cost.
  - drtgh 4y ago
    NAND cell modes: SLC 1-bit per cell, MLC 2-bit, TLC 3-bit, QLC 4-bit. And those cell modes are usually determined by the firmware/hardware controller of the NAND memory. The more bits stored per cell, the greater is the degradation. SLC-mode requires in average 2.2 times more erase cycles than MLC to achieve the same error rate [1]. So the differences in prices make it look as if some manufacturers are playing with us... [1] https://www.researchgate.net/publication/254005562_Software_controlled_cell_bit-density_to_improve_NAND_flash_lifetime https://www.researchgate.net/publication/254005562_Software_... PS: QLC-mode is the worst in all terms, the highest degradation and lower speed.
    - vbezhenar 4y ago
      Does it mean that with "raw" flash it's possible to use it in either mode? I guess it should not be impossible to create DIY SSD?
      - ilyt 4y ago
        It's essentially charging a cell to a level on write and measuring the voltage on read. So technically it's up to firmware to decide, assuming the hardware have stuff (ADC/DAC etc.) to handle it would be possible.
- drtgh 4y ago
  Not just SLC (1bit per cell). One thing that exasperates me is that one can't find even MLC drives anymore (2bits per cell), now everything is TLC or QLC (QLC sounds as a bad joke, how are they able to sell that thing?). A few years ago Samsung Pro SSDs were MLC disks, but suddenly they changed them to TLC. They are shameless for calling them 3bit-MLC that is pure oxymoron. 3bits per cell is TLC-mode, and the degradation is higher than a MLC-mode. Basically, it is a price increase by deceiving the consumer (to achieve this, they have reduced the characteristics of their other lines also. shameless).
  - myself248 4y ago
    The misnomer drives me nuts, it should be called 8LC or 16LC for the ever-finer states they have to resolve, and that would make the dismal endurance and reliability make sense.
NikolaNovak 4y ago
I don't understand this. Most laptops will have internal / ssd temperatures over 50C, and yet data usually lasts for years? >>"client class SSD must maintain its data integrity at the defined BER for only 500 hours at 52°C (less than 21 days) or 96 hours at 66°C (only four days)."
- schemester 4y ago
  Those are powered on when the laptop is on.
  - pclmulqdq 4y ago
    Also all of these are minimum requirements. They don't actually imply much, except about the state of technology when the statement was written. Flash has been improving very quickly on all axes.
    - jeffbee 4y ago
      And yet there are still people who will post about the good old days and the evils of MLC, as if current SSDs were not demonstrably better in every way.
      - ezconnect 4y ago
        I still remember the bubble memory system that would someday replace HDD back in the 80s
      - Robotbeat 4y ago
        They aren't. Write endurance is significantly lower than SLC, it's just compensated for by lots of write leveling.
        userbinator 4y ago
        More precisely, endurance and retention become exponentially lower with each additional bit stored per cell, while capacity only increases multiplicatively.
fbdab103 4y ago
Nuts! I have been thinking of leaving an emergency encrypted backup in my car, but evidently that is likely to self cook almost immediately. I assumed the lifetime was not great, but that is far more aggressive than I had feared.
- 7speter 4y ago
  Would it cook in the trumk (assuming your car has one)
  - usefulcat 4y ago
    In a warm climate the trunk is likely no better..
- sgtnoodle 4y ago
  Maybe use a 2.5" hard drive rather than an SSD? I can't think of any downsides for that purpose.
  - Dalewyn 4y ago
    Assuming the car is actually used, an HDD would be subject to numerous physical stresses. Not exactly something HDDs like.
    - upofadown 4y ago
      2.5" hard drives are usually very robust when powered down. That comes from the age when they were expected to be used in laptops.
      - gymbeaux 4y ago
        I was about to say “the age? You mean today” and realized 2.5” “laptop” hard drives aren’t really used in laptops anymore, even the low-end ones. Damn.
Helmut10001 4y ago
I cool my server to 30°-35° HDD temperatures, because that's supposed to increase their life. However, all my SSDs are then at 23-27° [1]. I think I saw some long endurance tests and they pointed out that failure rates for SSDs increase slightly below 25°. Tricky tradeoff. [1]: https://i.ibb.co/dtt6dwj/ssd-hdd-tmp.png https://i.ibb.co/dtt6dwj/ssd-hdd-tmp.png
- Dalewyn 4y ago
  HDDs and SSDs operate on fundamentally different technologies, so it shouldn't be a surprise that they desire vastly different environments to reside in.
  - sgtnoodle 4y ago
    I would think that over many years of iteration by engineers, both would converge on functioning reliably in the same environment. They're both intended to be integrated into computer systems after all.
    - Dalewyn 4y ago
      They do operate reliably in the same environment; what you're talking about is operating in ideal environments. When we're talking ideals, it shouldn't come as a surprise that two fundamentally different things desire two fundamentally different ideal environments.
      - sgtnoodle 4y ago
        I appreciate your distinction, but I still think my point stands. As the technology is iterated on and refined based on years of feedback from real world use, I would expect the ideal environment for a given class of technology to converge on the typical operating environment. Decisions will be made that shift the physical properties one way or another. Silicon will be doped with different impurities. Transistors will be made with different sizes and geometries. Different metals and plastics will be used. Different voltages will be applied. People desire practical technological solutions to serve their needs. A box of "spinning rust" doesn't desire much of anything. A CPU is just a rock that's better at arithmetic than another rock.

userbinator 4y ago

Is the 1-year spec after all the rated program/erase cycles have already been used, so the flash cells are worn and much "leakier"? That's still rather disturbing, since I have datasheets for NAND flash from around 2 decades ago that specify 10 years retention after 100K cycles (although probably at 25C), and some slightly newer ones with 5 years / 1.5K cycles (MLC); and also explains the increasing secrecy surrounding the flash industry. The very few I could find for TLC don't even mention retention and endurance is vaguely specified, and refer you to some, probably super-secret, qualification report for the actual numbers. Then again, perhaps I shouldn't be surprised ever since they came up with the misnomers that are "TLC" and now "QLC", and nearly drove SLC to extinction. I don't want 3x or 4x more storage for the same price (or 1/3 or 1/4 the price) if it's 1/8th or 1/16th exponentially more unreliable --- that's how the physics works and there's no way around that --- but that's what they seem to be pushing for. You can get $13 128GB TLC SSDs as mentioned in the article but I don't see any $39 128GB SLC SSDs being made, nor $13 ~40GB SLC SSDs, despite the fact that such a device would have the exact same cost per NAND cell (and as a bonus, be much faster and simpler since SLC needs much less ECC and advanced wear leveling algorithms than TLC/QLC.)

smartbit 4y ago
> but I don't see any $39 128GB SLC SSDs being made, nor $13 ~40GB SLC SSDs Shouldn’t it be 2^3 times more expensive than TLC? IOW a $104 128GB SLC SSD or a $13 16GB SLC SSD. Edit: guess you’re right userbinator
- userbinator 4y ago
  No. Each cell in TLC stores three bits (and has 8 actual voltage levels, hence the misnomer), and thus TLC should either be a third of the cost of SLC at the same density, or three times the density as SLC for the same cost.
- drtgh 4y ago
  NAND cell modes: SLC 1-bit per cell, MLC 2-bit, TLC 3-bit, QLC 4-bit. And those cell modes are usually determined by the firmware/hardware controller of the NAND memory. The more bits stored per cell, the greater is the degradation. SLC-mode requires in average 2.2 times more erase cycles than MLC to achieve the same error rate [1]. So the differences in prices make it look as if some manufacturers are playing with us... [1] https://www.researchgate.net/publication/254005562_Software_controlled_cell_bit-density_to_improve_NAND_flash_lifetime https://www.researchgate.net/publication/254005562_Software_... PS: QLC-mode is the worst in all terms, the highest degradation and lower speed.
  - vbezhenar 4y ago
    Does it mean that with "raw" flash it's possible to use it in either mode? I guess it should not be impossible to create DIY SSD?
    - ilyt 4y ago
      It's essentially charging a cell to a level on write and measuring the voltage on read. So technically it's up to firmware to decide, assuming the hardware have stuff (ADC/DAC etc.) to handle it would be possible.
drtgh 4y ago
Not just SLC (1bit per cell). One thing that exasperates me is that one can't find even MLC drives anymore (2bits per cell), now everything is TLC or QLC (QLC sounds as a bad joke, how are they able to sell that thing?). A few years ago Samsung Pro SSDs were MLC disks, but suddenly they changed them to TLC. They are shameless for calling them 3bit-MLC that is pure oxymoron. 3bits per cell is TLC-mode, and the degradation is higher than a MLC-mode. Basically, it is a price increase by deceiving the consumer (to achieve this, they have reduced the characteristics of their other lines also. shameless).
- myself248 4y ago
  The misnomer drives me nuts, it should be called 8LC or 16LC for the ever-finer states they have to resolve, and that would make the dismal endurance and reliability make sense.

NikolaNovak 4y ago

I don't understand this. Most laptops will have internal / ssd temperatures over 50C, and yet data usually lasts for years? >>"client class SSD must maintain its data integrity at the defined BER for only 500 hours at 52°C (less than 21 days) or 96 hours at 66°C (only four days)."

schemester 4y ago
Those are powered on when the laptop is on.
- pclmulqdq 4y ago
  Also all of these are minimum requirements. They don't actually imply much, except about the state of technology when the statement was written. Flash has been improving very quickly on all axes.
  - jeffbee 4y ago
    And yet there are still people who will post about the good old days and the evils of MLC, as if current SSDs were not demonstrably better in every way.
    - ezconnect 4y ago
      I still remember the bubble memory system that would someday replace HDD back in the 80s
    - Robotbeat 4y ago
      They aren't. Write endurance is significantly lower than SLC, it's just compensated for by lots of write leveling.
      - userbinator 4y ago
        More precisely, endurance and retention become exponentially lower with each additional bit stored per cell, while capacity only increases multiplicatively.

fbdab103 4y ago

Nuts! I have been thinking of leaving an emergency encrypted backup in my car, but evidently that is likely to self cook almost immediately. I assumed the lifetime was not great, but that is far more aggressive than I had feared.

7speter 4y ago
Would it cook in the trumk (assuming your car has one)
- usefulcat 4y ago
  In a warm climate the trunk is likely no better..
sgtnoodle 4y ago
Maybe use a 2.5" hard drive rather than an SSD? I can't think of any downsides for that purpose.
- Dalewyn 4y ago
  Assuming the car is actually used, an HDD would be subject to numerous physical stresses. Not exactly something HDDs like.
  - upofadown 4y ago
    2.5" hard drives are usually very robust when powered down. That comes from the age when they were expected to be used in laptops.
    - gymbeaux 4y ago
      I was about to say “the age? You mean today” and realized 2.5” “laptop” hard drives aren’t really used in laptops anymore, even the low-end ones. Damn.

Helmut10001 4y ago

I cool my server to 30°-35° HDD temperatures, because that's supposed to increase their life. However, all my SSDs are then at 23-27° [1]. I think I saw some long endurance tests and they pointed out that failure rates for SSDs increase slightly below 25°. Tricky tradeoff. [1]: https://i.ibb.co/dtt6dwj/ssd-hdd-tmp.png https://i.ibb.co/dtt6dwj/ssd-hdd-tmp.png

Dalewyn 4y ago
HDDs and SSDs operate on fundamentally different technologies, so it shouldn't be a surprise that they desire vastly different environments to reside in.
- sgtnoodle 4y ago
  I would think that over many years of iteration by engineers, both would converge on functioning reliably in the same environment. They're both intended to be integrated into computer systems after all.
  - Dalewyn 4y ago
    They do operate reliably in the same environment; what you're talking about is operating in ideal environments. When we're talking ideals, it shouldn't come as a surprise that two fundamentally different things desire two fundamentally different ideal environments.
    - sgtnoodle 4y ago
      I appreciate your distinction, but I still think my point stands. As the technology is iterated on and refined based on years of feedback from real world use, I would expect the ideal environment for a given class of technology to converge on the typical operating environment. Decisions will be made that shift the physical properties one way or another. Silicon will be doped with different impurities. Transistors will be made with different sizes and geometries. Different metals and plastics will be used. Different voltages will be applied. People desire practical technological solutions to serve their needs. A box of "spinning rust" doesn't desire much of anything. A CPU is just a rock that's better at arithmetic than another rock.