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Flash has to be powered so the contents of each cell can be refreshed so data isn't lost which make it a less than optimal solution for long term archival stora

Flash has to be powered so the contents of each cell can be refreshed so data isn't lost which make it a less than optimal solution for long term archival storage or offside backups. Simply storing the physical media is easier than maintaining and keeping secure systems to plug the flash devices into.

edoceo 5y ago
Can you put them in a battery powered box, with no data connection? I'm thinking my little consumer grade APC could power one for many days (months?). I'll have to check the numbers
- wtallis 5y ago
  You don't need to keep SSDs powered continuously. You just need to power them on periodically and read all the data on the drive so the SSD controller has the chance to notice data degradation and repair it before it becomes unrecoverable. This does not need to be done more often than once per year. For SSDs that are exclusively used for archival and thus never approach the end of their rated write endurance, it may be adequate to do this once per decade. Basically, any backup strategy that includes a sensible amount of testing and verification should suffice.
  - JaimeThompson 5y ago
    IBM, Samsung, Intel, and other manufactures of flash and flash based products disagree with you on that only once per year time frame. As flash gets more and more dense leakage from the cells becomes a much more difficult problem to solve.
    - wtallis 5y ago
      Last time I checked, those companies were still adhering to the JEDEC standards for how they define SSD write endurance, which is based on how worn-out the flash can be while still meeting certain unpowered data retention thresholds. For consumer SSDs, that threshold is one year unpowered and stored at 30°C. [1] All of the challenges of unpowered data retention are already being addressed in the normal course of bringing new generations of flash and SSDs to market, even though nobody is yet making drives specifically tailored for that use case. Additionally, lightly-used flash has error rates that are orders of magnitude smaller than flash that has reached or is approaching its write endurance limit. Which is why an archive-only SSD can very reasonably be expected to provide unpowered data retention far in excess of one year. [1] For enterprise drives, the specified duration is shorter but the storage temperature is higher. The warrantied write endurance is also typically higher, so those drives are willing to take their flash to a more thoroughly worn-out state.
- selfhoster11 5y ago
  At this point, you might as well just invest in a tape library
throw0101a 5y ago
> Flash has to be powered so the contents of each cell can be refreshed so data isn't lost That's not how flash storage works. You can unplug a flash drive and put it on a shelf and it will keep its data. Here's a review of portable, external SSDs that don't lose their data when not plugged in: * https://www.tomshardware.com/reviews/best-external-hard-drive-ssd,5987.html https://www.tomshardware.com/reviews/best-external-hard-driv... Are you thinking of DRAM perhaps?
- nisegami 5y ago
  No, they're referring to bit rot on flash storage due to slow leakage of the charge that represents the data. It occurs on long time scales, definitely years. But the more bits per cell (SLC vs TLC vs QLC), the more likely it is.
  - deleted 5y ago
    [deleted]
  - throw0101a 5y ago
    > No, they're referring to bit rot on flash storage due to slow leakage of the charge that represents the data. Could not the same be said of the magnetism of the bits on spinning rust? What's the shelf life of data on an HDD? Tapes also have magnetic charge, but are designed to be "unrefreshed" for longer periods of time.
    - labawi 5y ago
      Tapes and HDDs are magnetic. Flash and DRAM is electric. It is easier to create magnetically stable structures (magnets) than non-leaking capacitors. Flash has a better insulator than DRAM, but it wears out with use and leaks more with higher temperature, densities, less margin with more bits per cell...
- JaimeThompson 5y ago
  Depending on the design of the flash, the storage temperature, and other factors that data can rot. Please see [1] for one source. [1] https://www.ibm.com/support/pages/flash-data-retention-0 https://www.ibm.com/support/pages/flash-data-retention-0
selfhoster11 5y ago
That's what I'm thinking. If flash-based archives require servicing to keep their data, there are systems that provide far better trade-offs for similar amount of bother.
deleted 5y ago
[deleted]

edoceo 5y ago

Can you put them in a battery powered box, with no data connection? I'm thinking my little consumer grade APC could power one for many days (months?). I'll have to check the numbers

wtallis 5y ago
You don't need to keep SSDs powered continuously. You just need to power them on periodically and read all the data on the drive so the SSD controller has the chance to notice data degradation and repair it before it becomes unrecoverable. This does not need to be done more often than once per year. For SSDs that are exclusively used for archival and thus never approach the end of their rated write endurance, it may be adequate to do this once per decade. Basically, any backup strategy that includes a sensible amount of testing and verification should suffice.
- JaimeThompson 5y ago
  IBM, Samsung, Intel, and other manufactures of flash and flash based products disagree with you on that only once per year time frame. As flash gets more and more dense leakage from the cells becomes a much more difficult problem to solve.
  - wtallis 5y ago
    Last time I checked, those companies were still adhering to the JEDEC standards for how they define SSD write endurance, which is based on how worn-out the flash can be while still meeting certain unpowered data retention thresholds. For consumer SSDs, that threshold is one year unpowered and stored at 30°C. [1] All of the challenges of unpowered data retention are already being addressed in the normal course of bringing new generations of flash and SSDs to market, even though nobody is yet making drives specifically tailored for that use case. Additionally, lightly-used flash has error rates that are orders of magnitude smaller than flash that has reached or is approaching its write endurance limit. Which is why an archive-only SSD can very reasonably be expected to provide unpowered data retention far in excess of one year. [1] For enterprise drives, the specified duration is shorter but the storage temperature is higher. The warrantied write endurance is also typically higher, so those drives are willing to take their flash to a more thoroughly worn-out state.
selfhoster11 5y ago
At this point, you might as well just invest in a tape library

throw0101a 5y ago

> Flash has to be powered so the contents of each cell can be refreshed so data isn't lost That's not how flash storage works. You can unplug a flash drive and put it on a shelf and it will keep its data. Here's a review of portable, external SSDs that don't lose their data when not plugged in: * https://www.tomshardware.com/reviews/best-external-hard-drive-ssd,5987.html https://www.tomshardware.com/reviews/best-external-hard-driv... Are you thinking of DRAM perhaps?

nisegami 5y ago
No, they're referring to bit rot on flash storage due to slow leakage of the charge that represents the data. It occurs on long time scales, definitely years. But the more bits per cell (SLC vs TLC vs QLC), the more likely it is.
- deleted 5y ago
  [deleted]
- throw0101a 5y ago
  > No, they're referring to bit rot on flash storage due to slow leakage of the charge that represents the data. Could not the same be said of the magnetism of the bits on spinning rust? What's the shelf life of data on an HDD? Tapes also have magnetic charge, but are designed to be "unrefreshed" for longer periods of time.
  - labawi 5y ago
    Tapes and HDDs are magnetic. Flash and DRAM is electric. It is easier to create magnetically stable structures (magnets) than non-leaking capacitors. Flash has a better insulator than DRAM, but it wears out with use and leaks more with higher temperature, densities, less margin with more bits per cell...
JaimeThompson 5y ago
Depending on the design of the flash, the storage temperature, and other factors that data can rot. Please see [1] for one source. [1] https://www.ibm.com/support/pages/flash-data-retention-0 https://www.ibm.com/support/pages/flash-data-retention-0

selfhoster11 5y ago

That's what I'm thinking. If flash-based archives require servicing to keep their data, there are systems that provide far better trade-offs for similar amount of bother.

deleted 5y ago

[deleted]