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At a conference, I once met somebody who said his team had the joy of dismantling broken SD cards and figuring out why they broke. One of the anecdotes I disti

At a conference, I once met somebody who said his team had the joy of dismantling broken SD cards and figuring out why they broke. One of the anecdotes I distinctly recall was about a batch of cards that (for obvious cost saving reasons) used the actual data flash to store its own firmware as well. IIRC due to a bug in the wear leveling accounting, once the card got sufficiently full, the wear leveling code ended up partially overwriting the firmware itself.

billpg 2y ago
I recall once having an SD card with a mysterious file in the root folder with system and hidden attributes on it. I decided to delete the file and some time later (months), the card suddenly stopped working. It maybe stopped working once the OS decided the bytes were available for use (which it would only have done without the file marking that space as unavailable) and overwrote that section. I suspect defragmenting or otherwise moving the file about for whatever reason would have had the same effect.
- karamanolev 2y ago
  Wouldn't a regular filesystem format of the card have the same effect - wipe the file? Wouldn't such SD cards be fatally flawed for most applications? My camera, drone, etc. all format the cards.
  - billpg 2y ago
    I vaguely recall thinking the file was just some sort of serial number or stock tracking metadata when I deleted it. It might have instead failed for quite mundane reasons such as low quality manufacture. I don't know. Exposing the firmware in this fashion would be a bad idea for all of these reasons. It is a good thing that SD card manufacturers don't do this any more, if they ever did.
    - vardump 2y ago
      Firmware definitely would not be on the filesystem layer or even accessible on the block device.
      - 01HNNWZ0MV43FF 2y ago
        You'd think yeah
        tiberious726 2y ago
        It isn't. Before a chip has firmware loaded, it can't decode filesystems.
        15155 2y ago
        Even after a chip has firmware loaded, which controller can make logical sense of a filesystem?
        goodburb 2y ago
        According to SDXC specs, the controller looks for exFAT markers to relocate the table and bitmap to smaller AU units. exfatprogs can pack bitmap with table for SDHC and lower: https://manpages.debian.org/experimental/exfatprogs/mkfs.exfat.8.en.html https://manpages.debian.org/experimental/exfatprogs/mkfs.exf...
        samatman 2y ago
        That doesn't at all mean that the firmware can't be exposed through the filesystem. Is that a bad idea? Almost certainly. Is it possible? Absolutely yes.
Sakos 2y ago
Man, I'd love to work in that team for a year. I've had so many SD cards fail on me (most recently a 1TB SanDisk Extreme which was used in my Steam Deck) and it feels like most of them are junk.
- robotnikman 2y ago
  IIRC the denser the memory on the cards, the more likely problems are to arise. I forget the specifics but it has to do with the physics involving electronics on such a small scale. That's why industrial grade cards tend to be in much smaller capacities, but they are much longer lasting.
  - Sakos 2y ago
    I wish we'd move away from microSD cards to a larger format if it meant more durable storage. I hate these things. I just end up keeping them in an SDcard adapter when they're not in active use so I don't lose them. USB sticks seem to have the same issue with durability though. I've also had multiple of those fail on me. I'm currently eyeing those SSD USB sticks and I wonder how much more durable they might be.
    - robotnikman 2y ago
      The regular SD card form factor seems great when it comes to more durable storage, but obviously would not be ideal for smaller devices. I've heard that many USB sticks use lower quality binned chips so that may be why they usually fail more often despite their size, but this is just anecdotal from what I've heard.
- chasil 2y ago
  I read elsewhere here that if you fdisk/gdisk a partition that is one third of the drive and limit yourself to that space, then the drive will exhibit the reliability of SLC media, and last far longer than rated.
2Gkashmiri 2y ago
Have an SD card that was copying file on to and in the middle of transfer the card went kaput and hasnt seen since. No machine I try it on even acknowledges it existence. The card is almost a decade old at this point but is there a way to recover data ?
- robotnikman 2y ago
  Best to consult a data recovery specialist, will cost you an arm and a leg though. 10 years without power makes me think most of it wont be recoverable even if they can get to the data on it, but then again it depends on a lot of factors when it comes to flash memory.
  - eschneider 2y ago
    Some amount of the data is almost certainly recoverable, but getting it done commercially is going to be $$$.
  - goodburb 2y ago
    IIRC SD cards and most SSDs don't go through error check routine when powered, it has to be specified. Some do use the power-on time and run a routine if left on for too long. You usually you have to read the entire drive to maintain, in my case S.M.A.R.T. reported changes to reserve blocks after doing that on an old drive. I have a 16 year old 4GB SDcard with all data still intact.
  - 2Gkashmiri 2y ago
    10 years in use. On a phone.
- mystified5016 2y ago
  Sometimes you can recover data over the SPI interface instead of the proprietary SD interface. Essentially, plug it into an arduino with one of the many SD card libraries and slowly dump the data over the serial link. I'm unsure if this is just urban legend or not, though. I've never tried myself.

billpg 2y ago

I recall once having an SD card with a mysterious file in the root folder with system and hidden attributes on it. I decided to delete the file and some time later (months), the card suddenly stopped working. It maybe stopped working once the OS decided the bytes were available for use (which it would only have done without the file marking that space as unavailable) and overwrote that section. I suspect defragmenting or otherwise moving the file about for whatever reason would have had the same effect.

karamanolev 2y ago
Wouldn't a regular filesystem format of the card have the same effect - wipe the file? Wouldn't such SD cards be fatally flawed for most applications? My camera, drone, etc. all format the cards.
- billpg 2y ago
  I vaguely recall thinking the file was just some sort of serial number or stock tracking metadata when I deleted it. It might have instead failed for quite mundane reasons such as low quality manufacture. I don't know. Exposing the firmware in this fashion would be a bad idea for all of these reasons. It is a good thing that SD card manufacturers don't do this any more, if they ever did.
  - vardump 2y ago
    Firmware definitely would not be on the filesystem layer or even accessible on the block device.
    - 01HNNWZ0MV43FF 2y ago
      You'd think yeah
      - tiberious726 2y ago
        It isn't. Before a chip has firmware loaded, it can't decode filesystems.
        15155 2y ago
        Even after a chip has firmware loaded, which controller can make logical sense of a filesystem?
        goodburb 2y ago
        According to SDXC specs, the controller looks for exFAT markers to relocate the table and bitmap to smaller AU units. exfatprogs can pack bitmap with table for SDHC and lower: https://manpages.debian.org/experimental/exfatprogs/mkfs.exfat.8.en.html https://manpages.debian.org/experimental/exfatprogs/mkfs.exf...
        samatman 2y ago
        That doesn't at all mean that the firmware can't be exposed through the filesystem. Is that a bad idea? Almost certainly. Is it possible? Absolutely yes.

Sakos 2y ago

Man, I'd love to work in that team for a year. I've had so many SD cards fail on me (most recently a 1TB SanDisk Extreme which was used in my Steam Deck) and it feels like most of them are junk.

robotnikman 2y ago
IIRC the denser the memory on the cards, the more likely problems are to arise. I forget the specifics but it has to do with the physics involving electronics on such a small scale. That's why industrial grade cards tend to be in much smaller capacities, but they are much longer lasting.
- Sakos 2y ago
  I wish we'd move away from microSD cards to a larger format if it meant more durable storage. I hate these things. I just end up keeping them in an SDcard adapter when they're not in active use so I don't lose them. USB sticks seem to have the same issue with durability though. I've also had multiple of those fail on me. I'm currently eyeing those SSD USB sticks and I wonder how much more durable they might be.
  - robotnikman 2y ago
    The regular SD card form factor seems great when it comes to more durable storage, but obviously would not be ideal for smaller devices. I've heard that many USB sticks use lower quality binned chips so that may be why they usually fail more often despite their size, but this is just anecdotal from what I've heard.
chasil 2y ago
I read elsewhere here that if you fdisk/gdisk a partition that is one third of the drive and limit yourself to that space, then the drive will exhibit the reliability of SLC media, and last far longer than rated.

2Gkashmiri 2y ago

Have an SD card that was copying file on to and in the middle of transfer the card went kaput and hasnt seen since. No machine I try it on even acknowledges it existence. The card is almost a decade old at this point but is there a way to recover data ?

robotnikman 2y ago
Best to consult a data recovery specialist, will cost you an arm and a leg though. 10 years without power makes me think most of it wont be recoverable even if they can get to the data on it, but then again it depends on a lot of factors when it comes to flash memory.
- eschneider 2y ago
  Some amount of the data is almost certainly recoverable, but getting it done commercially is going to be $$$.
- goodburb 2y ago
  IIRC SD cards and most SSDs don't go through error check routine when powered, it has to be specified. Some do use the power-on time and run a routine if left on for too long. You usually you have to read the entire drive to maintain, in my case S.M.A.R.T. reported changes to reserve blocks after doing that on an old drive. I have a 16 year old 4GB SDcard with all data still intact.
- 2Gkashmiri 2y ago
  10 years in use. On a phone.
mystified5016 2y ago
Sometimes you can recover data over the SPI interface instead of the proprietary SD interface. Essentially, plug it into an arduino with one of the many SD card libraries and slowly dump the data over the serial link. I'm unsure if this is just urban legend or not, though. I've never tried myself.