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Several Questions on Sentry Mode

This will be a bit of a long post so I will number my different questions:


1) I did not get the USB stick that has wifi (the particular one that many of the tesla youtubers have reviewed) instead I got a high endurance microsd card along with an adapter.

Just after my first trip with it and consequently getting my first "Sentry incident" I tried sifting through the UI of the center screen and was unable to find any way to natively review the Sentry incident before I left the parking lot.

So short of getting the wifi enabled usb, is there any dongle or adapter that I can use to plug my current microsd adapter into my iphone, and use one of the Dashcam apps to view the incident right then and there in my car before leaving?




2) For the times when I want to come home and view the Sentry clips on the larger screen of my desktop, when I open up the "SentryClips" folder, I notice there are 10 minute chunks of time, lets say for example starting at 9:30pm - 9:40pm, does that mean the Sentry "incident" happened at the first minute of that 10 minute chunk?

OR what Im thinking could also happen is that it happens more like in the middle of the 10 minute chunk, so the "incident" happened at 9:35pm, and so then the Sentry mode takes the previous 5 minutes of what is technically the dashcam footage, and the goes on to capture the next 5 minutes of footage, to result in the 10 minute chunk of footage that we see marked as a single Sentry incident.




3) I accidentally and stupidly just pulled out the USB adapter from the Model 3 USB port without first holding my finger on the dashcam icon with illuminated red light, and so right when I pulled the adapter out I remember hearing about how if you do that it can corrupt the drive irreversibly and you will be forced to buy a new one, well so then I plugged it into my desktop computer, and a window popped up saying something to the effect of how Windows will need to scan it since there was some sort of error before opening up the folder, and after a few seconds of scanning Windows said everything was alright with it, and lo and behold I was able to successfully access everything on the microsd without issue.

So it seems like I got lucky that nothing was corrupted, HOWEVER I wanted to know if even though nothing seemed corrupted as I was able to access the "Recentclips" and "SentryClips" folders (of course I didnt actually sift through every single video) is it possible that in the future that it will spontaneously become corrupted because of the one time that I accidentally pulled the adapter out without safely ejecting first?




4) Is the mechanism by which the Tesla dashcam (and perhaps other dashcams as well) operates, by continuously taking footage whenever the car is on, just filling up space until the entire 256gb is filled, and then at which point it will then go back to the very beginning and chronologically begin to overwrite the earliest footage with the newest footage, and this trend continues up until 256gb is completely overwritten, and so on and so forth?




Sorry for the long post!
 

srs5694

Active Member
Jan 15, 2019
1,287
1,620
Woonsocket, RI
So short of getting the wifi enabled usb, is there any dongle or adapter that I can use to plug my current microsd adapter into my iphone, and use one of the Dashcam apps to view the incident right then and there in my car before leaving?

Yes, there are adapters to enable you to plug USB devices into iPhones. A search on eBay turns up a bunch. A caveat, though: I've never used these specific items, but I do have a couple of similar adapters to enable me to plug a USB flash drive into my USB-C-based Android phone, and that works fine. I assume that the iPhone equivalent would work as well, but I've never tried one.

FWIW, I've also seen USB drives that include both USB and iPhone connectors. Something like that should work as well, provided it's big enough, reliable enough, etc.

2) For the times when I want to come home and view the Sentry clips on the larger screen of my desktop, when I open up the "SentryClips" folder, I notice there are 10 minute chunks of time, lets say for example starting at 9:30pm - 9:40pm, does that mean the Sentry "incident" happened at the first minute of that 10 minute chunk?

No, it's more likely to have occurred in the final minute or two of the recording.

3) I accidentally and stupidly just pulled out the USB adapter from the Model 3 USB port without first holding my finger on the dashcam icon with illuminated red light, and so right when I pulled the adapter out I remember hearing about how if you do that it can corrupt the drive irreversibly and you will be forced to buy a new one

This is unlikely. First, be aware that there are (broadly speaking, and slightly simplifying) two types of problems that might occur: hardware faults and filesystem damage. What you've described ("corrupt the drive irreversibly") would be a hardware fault. This could happen if there's some stray voltage or some other thing that damages the drive. USB was explicitly designed to minimize the chances of such problems occurring, so they're very unlikely to be triggered by pulling the drive, whether or not it's actively recording at that moment. That said, some USB memory devices are simply cheap {expletive deleted} from China that won't last long under heavy use, which the Tesla Sentry Mode and TeslaCam will impose on the device. I also can't rule out the possibility that some poorly-designed USB drive would be damaged by being pulled when an active write was occurring; but USB devices should be designed to not self-destruct when that happens. The more common problem is filesystem damage, which can happen when the data structures are left in an inconsistent state. When filesystem damage occurs, you may lose some recordings, or even be unable to store more recordings; but it's always possible to keep using the device by repairing the filesystem or, in a worst-case scenario, re-creating the filesystem (which will render any data on it inaccessible).

As of a few months ago, the was no way to safely unmount a USB drive from a Tesla. I say this because my own observation has been that the "dirty bit" on the filesystem has always been set when I examine my own USB drives after they've been used in the Tesla. The "dirty bit" indicates that the filesystem is in use; it should be cleared when a filesystem is unmounted (aka "safely ejected" or similar terms). Its presence when the OS tries to mount the drive indicates that there may be filesystem damage. If the USB device is not safely unmounted before pulling the drive, there will always be some chance of damaging the filesystem. Even stopping recording does not unmount the filesystem, although stopping recording and waiting a few seconds is likely to cause the Tesla to flush the filesystem buffers and leave it in a consistent state (aside from the "dirty bit" being set), which is likely to reduce the odds of filesystem damage. There are some hints that Tesla may be performing filesystem checks whenever you plug in a USB drive, which should further help minimize the risk of problems developing, since a small problem will be less likely to grow into a big one.

Overall, I recommend performing a filesystem check after pulling a TeslaCam drive but before mounting it on your computer; however, this is difficult with most modern OSes, which try to auto-mount filesystems as soon as you plug in a device. At a minimum, you should be aware of the issue and be prepared to run a filesystem check if the OS complains about the state of the drive or if anything looks weird on the drive.

4) Is the mechanism by which the Tesla dashcam (and perhaps other dashcams as well) operates, by continuously taking footage whenever the car is on, just filling up space until the entire 256gb is filled, and then at which point it will then go back to the very beginning and chronologically begin to overwrite the earliest footage with the newest footage, and this trend continues up until 256gb is completely overwritten, and so on and so forth?

Not quite. The Tesla will record up to one hour (IIRC) of footage, in files sized to hold one minute's worth of footage. Once the one-hour point is hit, the Tesla will delete one minute's worth of footage before recording the next one, and so on. If Sentry Mode detects an "event" or if you hit the button to save a TeslaCam recording, the car moves ten minutes' worth of footage to its SavedClips directory and continues recording. Thus, the drive won't actually fill up unless and until a lot of clips get saved. A bigger drive has the advantage that it can save more clips. Also, a bigger drive means that any given sector of the drive will be recorded to less often, so a bigger drive should last longer than a smaller one, assuming they're of otherwise equal quality.
 
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Not quite. The Tesla will record up to one hour (IIRC) of footage, in files sized to hold one minute's worth of footage. Once the one-hour point is hit, the Tesla will delete one minute's worth of footage before recording the next one, and so on. If Sentry Mode detects an "event" or if you hit the button to save a TeslaCam recording, the car moves ten minutes' worth of footage to its SavedClips directory and continues recording. Thus, the drive won't actually fill up unless and until a lot of clips get saved. A bigger drive has the advantage that it can save more clips. Also, a bigger drive means that any given sector of the drive will be recorded to less often, so a bigger drive should last longer than a smaller one, assuming they're of otherwise equal quality.


Thanks you so much for taking the time to explain it all to me!

I understood everything, I just want to know if it would help increase the life of the Sandisk microsd card if I periodically wipe it clean instead of having the card overwrite by itself?
(or would that make things worse?)
 

Knightshade

Well-Known Member
Jul 31, 2017
15,440
28,956
NC
Thanks you so much for taking the time to explain it all to me!

I understood everything, I just want to know if it would help increase the life of the Sandisk microsd card if I periodically wipe it clean instead of having the card overwrite by itself?
(or would that make things worse?)


An endurance card (assuming you didn't get a tiny one) should be good for decades given the relatively tiny amount of data dashcam actually writes.

It's honestly overkill for this application.
 

srs5694

Active Member
Jan 15, 2019
1,287
1,620
Woonsocket, RI
Thanks you so much for taking the time to explain it all to me!

I understood everything, I just want to know if it would help increase the life of the Sandisk microsd card if I periodically wipe it clean instead of having the card overwrite by itself?
(or would that make things worse?)

Depending on the nature of "wipe it clean," it would have either little effect or make it very slightly worse.

A simple "wipe it clean" operation would involve creating a fresh filesystem directly over the old one. (It might also involve creating a fresh partition table.) At a low level, this operation would involve writing a few sectors' worth of data to the drive, which will have a negligible impact on the health of the drive. It would not improve matters from a longevity point of view; whether or not you write a fresh filesystem in this way, the same video data will be written to the drive, in more-or-less the same way; there will just be a change in what specific sectors are written vs. not creating a fresh filesystem. That said, creating a fresh filesystem periodically might help combat filesystem damage, should it accumulate for some reason. Then too, a filesystem check should have the same effect.

A more complete "wipe it clean" operation might involve writing sectors filled with "0" values or random data to the entire drive. This type of operation is sometimes done to ensure that any sensitive data are wiped out before selling or disposing of a disk. In the case of a USB flash drive that you're keeping, though, the security benefits will be nil, unless you're concerned about theft and the drive held some sensitive data in the past. Rather, this type of activity will simply serve to put an unnecessary write cycle on every sector of the device. In theory, that should degrade the drive slightly, but the amount should be quite slight -- it's just one write operation, after all. If the drive was on the verge of failing, or have sectors that have already gone bad, this might push it over the top or make the failure apparent, which I suppose has some benefit, especially if you suspect the drive is going bad. It's not really a preventative measure in the usual sense, though. Note that wiping the drive in this way is likely to take quite a few minutes, whereas a simple filesystem creation operation will take a matter of a few seconds at most.
 
On a related note - I get 3 or so Sentry Mode events every time I park in a car park. I guess it is sensitive enough that it triggers even if a car parks next to me? I was expecting Sentry Mode to only trigger if my car touched or jostled. With so many ‘false alarms’ it’s frustrating.
 

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