The card’s partition structure in Hard Disk Sentinel. The card’s file system properties in Windows. It uses a very basic MBR (Master Boot Record) partition structure, with the first sector being the bare minimum to be recognized as a valid structure. The card is formatted as exFAT, with a 16 MB offset (that is, the first 16 MB of the card is unallocated), with an allocation unit size of 128 kilobytes. Android used to be able to do this as well, but nowadays it’s not possible without a rooted operating system. These information files are found in /sys/block/mmcblk X/device, where X is usually 0 depending on your host machine. Using an older laptop with a true SD-compliant slot (most newer ones are just USB card readers internally), I was able to grab the card’s metadata from Linux. The Flash should easily withstand thousands of write cycles without much issue. It turns out they used 3D TLC NAND, which is still quite durable and reliable due to the use of larger process geometries. UPDATE (July 19, 2020): I got my paws on another card (the 128GB variant), and did some reverse-engineering work on it to determine what Flash SanDisk used. Maybe I’ll buy another card to try this on… As much as I am tempted to remove the epoxy coating that covers the manufacturing test pads in order to get a NAND Flash signature directly, I like having a warranty for at least a few years. This is more in line with traditional 2D TLC NAND Flash, so I suspect that this rating is either based on different bitrates, or SanDisk is being really, really conservative in their estimates – or heck, maybe this really is just TLC NAND Flash that’s being configured and/or warrantied differently by SanDisk. Therefore, we get a final calculated P/E (program-erase) cycle count of… 936 cycles. A “64-gigabyte” card is really 59.605 binary gigabytes (“ gibibytes“) in capacity, but in this blog post I’m using the Windows notation of gigabytes that is, calculating in binary but displaying as decimal. Memory cards, like other block-based storage media, often define capacities with decimal prefixes, whereas computers usually binary. With a rating of 5,000 hours at this data rate, we get a specified endurance of 57,128.91 gigabytes written, or 55.79 terabytes written (TBW). This equates to 11,700 megabytes per hour, or 11.426 gigabytes per hour. SanDisk’s card packaging defines Full HD video to be 26 Mbps, which is equivalent to 3.25 (binary) megabytes per second. However, we can infer a rating with a little bit of math. Unfortunately, the endurance specifications for these cards are (probably intentionally) vague, only providing a set number of hours of video recording. SanDisk’s lineup of high-endurance memory cards are designed for use in very write-intensive workloads, such as constant video recording. The packaging also includes a license key for a 1-year subscription to the RescuePRO data recovery software (although in all honesty, you’d be better off using the free PhotoRec software instead). The paper-and-plastic package includes a small blister pack that holds the microSD card itself and the full-size SD card adapter, without a carrying case (granted, the memory card is expected to stay inside the dashcam for most of its working life). The card’s packaging isn’t much different than SanDisk’s typical microSD card offerings. I purchased the 64-gigabyte model, the SDSQQNR-064G-G46A. The solution: high-endurance memory cards! These cards (at least in theory) use more durable MLC or even SLC NAND Flash, which can take many more write cycles. In fact, SanDisk specifically denounces this line of cards for use in continuous-recording applications. Not only does the card have to endure temperature extremes, the constant writes can burn through the Flash’s write cycles in short order. However, not all cards are created equal.Ĭheaper cards, like SanDisk’s Ultra lineup, use cheaper TLC (triple-level cell) NAND Flash that is ill-suited to the harsh working conditions of a dashcam. Like any modern device, they generally use SD or microSD cards as their storage medium. UPDATE (July 19, 2020): I’ve analyzed a 128GB version of the High Endurance card, and it appears that SanDisk is using 3D TLC Flash.ĭashcams: they can be a crucial tool when reconstructing events in a vehicular incident, or a source of entertainment when watching compilations on YouTube.
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