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Dashcam Flash Drive - Volume Error on Plugging Drive Into Windows (10)

Discussion in 'Model 3' started by galan, Jul 20, 2019.

  1. galan

    galan Member

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    I'm not sure if this has been covered by another post or not...

    After formatting my flash drive to FAT32 and plugging it into my M3SR+, the drive mounted and worked ok. However, after stopping the dashcam recordings (as prescribed by Tesla), removing the drive and then plugging it into my Windows 10 computer, I got an error message from Windows stating that the volume (flash drive) has errors. This has happened multiple times. Windows prompts to fix the errors, which I say yes to, and all is fine, until the next time I take the flash drive out of the car, where I get the exact same error. It doesn't matter which flash drive I use: I have many different types and sizes; I always get the same Windows error.
    I decided to change my approach. I purchased an Western Digital external 2TB USB hard drive, hoping that changing the physical device itself might get rid of the error and also reduce the number of times I had to take a flash drive out for file deletions when the drive was getting full.
    It took a while to experiment before I got the 2TB drive to be accepted by the car and the volume mounted. (For those that are interested, I had to set the file cluster size to 65536 as it seems the car's software has a volume geometry issue if it is set to 32768 for a 2TB drive. The partition manager I used for formatting the drive to FAT32 was a free download).
    I put the (2TB) drive into the car and enabled the dashcam and went for a short drive, and also enabled Sentry mode when parked. When I got home, I stopped the drive (again as prescribed) and took it into my Windows computer. Guess what? Windows tossed exactly the same volume error message as before. So, clearly it has nothing to do with flash drive technology.
    I inspected the drive with my partition software, and it identified the problem as being a mismatch between the Partition Primary Boot Sector and the Copy (of) Boot Sector. Looking at both, the byte at offset 41h in the Primary Boot Sector had been changed from its initialized state of 0 (zero) to a 1 (one). Offset 41h in the volume boot sector is identified as "Unused". This byte can only have been changed while the drive was in the car, which means that Tesla's dashcam or Sentry mode software is changing it. The volume boot sector is basically inviolate and should not be written into by a software program as the consequences of doing so are totally unknown, especially if another piece of software tries to use it too. This seems to be a programming error by Tesla.
    When you tell Windows to "repair/fix" the volume, Windows sets this value back to 0 (zero) in the Primary Boot Sector, and you can unplug and replug the drive in and there are no errors (before putting back in the car). I tried setting the Copy Boot Sector value to 1 (one) so that the two boot sectors matched and Windows declared again that there errors on the volume. After telling Windows to fix the volume, it reset the Primary Boot Sector (41h) back to 0 (zero) and was not concerned that the Copy Boot Sector did not match, so the flagging by the partition manager software is unimportant, unless you want to use the Copy Boot Sector to recover a corrupt Primary Boot Sector.
    Notes:
    - The Windows volume error message is a volume integrity message and does not prevent you in any way from viewing any of the recorded files on the flash drive
    - I doubt that there is any relationship between this change to the Primary Boot Sector and the corrupt video files that many of us have experience.
    - I am hoping that road lumps and bumps will not cause a head crash on the WD external drive. I got it on sale for C$80 (US$60), so not a huge outlay if any problems. I used Command brand velco strips to attach it to the front wall of the front storage box (see pic) to stop it moving around.

    Pictures:
    After drive initialization and formatting
    View attachment 432228

    After drive removal from car


    Installation
     
  2. galan

    galan Member

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    Location:
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    Repost of pictures re my posting "Dashcam Flash Drive - Volume Error on Plugging Drive Into Windows (10)"

    Pictures:
    1. After drive initialization and formatting 2. After drive removal from car. 3. External drive installation
    WD 2TB FAT32 Cluster 65536 2019-07-18 1424-4.png WD 2TB FAT32 Cluster 65536 2019-07-18 1500-5.png WD External Drive Installation.jpeg
     
  3. ZOMGVTEK

    ZOMGVTEK Member

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    'Merica
    Mounting that drive vertically is probably the worst orientation. It may have been damaged, the standard consumer external drives are not particularly durable. A solid state drive is highly recommended. I don’t believe externals have accelerometers to dock the head when it’s subject to shock like most laptops do. A hard bump can send the head flying and damage it or the platters.
     
  4. Knightshade

    Knightshade Well-Known Member

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    The tesla has no way to cleanly unmount a drive before removing it.

    This is a Tesla SW issue, not a hardware issue.


    Also don't use a spinning drive in a car. Go back to some form of flash (USB key, SDcard, SSD, doesn't really matter for a decently large enough storage device- all are more than fast enough with more than enough write cycles for the typical ownership of a car)
     
  5. galan

    galan Member

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    The primary focus of my post was the volume error dialogue that Windows throws, not the use of an external drive.

    I clearly indicated in the last line of my post that I could have a head crash on the drive, which was a warning to others who might consider trying this (if they haven't already). I did not and I am certainly not advocating others do this; it is an experiment that might work or fail. If it fails, it is no big deal for me given the price I paid for the drive, and I will simply revert to a flash drive.

    Large SSD drives are just too expensive at this time, so for me they are a non-starter.

    Regarding vertical mounting, I already have two multi-terabyte NAS drives in my home environment that stand upright (book mode), and that is the way they are sold by the vendor. I have never had a problem with vertically mounted drives in all my years in IT.
     
  6. galan

    galan Member

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    Location:
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    Yes, it is a Tesla SW issue, which is what I said in my post; I never indicated it was a hardware issue.

    I do not agree with your contention that Tesla has no way to cleanly dismount a drive. For two reasons:
    (1) If Tesla can mount a drive for writing (to), they can certainly dismount a drive;
    (2) The act of pressing the dashcam icon is a directive to the underlying software interface to either mount, enable recording, download recordings, or dismount the USB drive.
    Secondly, It is unclear if the software problem relates to dismounting the volume or it is simply a programming error by Tesla in setting a flag that it shouldn't put in the Primary Boot Sector: I think it is the latter. As a side note, I used to write (operating) systems software, including disk drivers.

    Regarding alternative media, for me the issue is not about a media's read/writing life-cycle, it is about the file management and disk maintenance activities associated with smaller media sizes. It is a pain to have to keep taking a drive out and cleaning up the files.
     
  7. Knightshade

    Knightshade Well-Known Member

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    Apologies if I was unclear.

    The car is running Linux. Linux certainly can unmount a drive.

    But Tesla does not include doing so in any of their code around this feature- and offers no way for the user of the car to instruct the vehicle to do so.

    Pressing the button to stop recording does not unmount the drive, hence why pulling it out leaves the drive "dirty" when you insert it into a computer that scans it.

    Since the car isn't, ever, booting off the USB drive I can't imagine why there'd be any code at all that writes to the boot sector.



    Since Sentry events never over-write you will need to do that regardless from time to time, it's just a question of how often (and is more dependent on how busy the areas you use Sentry mode than anything else)- for example one user here filled a 32GB drive in 8 hours of parking at a busy lot at work.

    At that rate a 2TB drive would fill up roughly every 2 months (maybe less as we've no idea how early into the 8 hours his drive was actually full)
     

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