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Flash endurance gets a sort of odd amount of discussion on the Internet, and this adds to the small amount of public data from running lots of Flash devices to

Flash endurance gets a sort of odd amount of discussion on the Internet, and this adds to the small amount of public data from running lots of Flash devices to exhaustion. (MicroSD != SSD, of course, but it's something.) Seems possible that by charting it, you could find a "bathtub curve" (early failures/steady state/failures due to use) of failures, probably more than one curve breaking up by category--tiny "industrial" cards made for endurance are unsurprisingly surviving the longest, and counterfeits and (some but not all!) unknown brands are at the bottom. It would be interesting to also see the data on cards that haven't failed yet, i.e. how many write cycles they've survived so far. (You can sort the table at https://www.bahjeez.com/the-great-microsd-card-survey/all-microsd-card-results/ https://www.bahjeez.com/the-great-microsd-card-survey/all-mi... by cycles until first error to see what I mean. Love the Bart Simpson card coming in at #8.) One thing the reported averages already show, which is more about reliability stats in general than about Flash, is that the average write cycles survived is way higher than, say, the cycle count after which you'd see 5% of devices fail. The lower "n% will fail" number might be what informs the TBW spec on the box. So if you're able to handle failures gracefully and run drives 'til they drop, that probably adds substantially to how long you can run each device.

userbinator 1y ago
One thing the reported averages already show, which is more about reliability stats in general than about Flash, is that the average write cycles survived is way higher than, say, the cycle count after which you'd see 5% of devices fail. These endurance tests aren't testing retention much at all; they answer the question "how many cycles can the flash go through before it can't hold data for the very short amount of time it takes to read it back again on the next pass", which is not surprisingly much higher than e.g. the number of cycles before which the data will disappear after 3 months. The cells can be so worn and leaky they erase themselves within a few hours, but as long as that's more time than it takes until the data is read back, this test will still consider that successful.
- mikaey 1y ago
  Absolutely a fair point, and that's something that I've thought about for a follow-up study.

userbinator 1y ago

One thing the reported averages already show, which is more about reliability stats in general than about Flash, is that the average write cycles survived is way higher than, say, the cycle count after which you'd see 5% of devices fail. These endurance tests aren't testing retention much at all; they answer the question "how many cycles can the flash go through before it can't hold data for the very short amount of time it takes to read it back again on the next pass", which is not surprisingly much higher than e.g. the number of cycles before which the data will disappear after 3 months. The cells can be so worn and leaky they erase themselves within a few hours, but as long as that's more time than it takes until the data is read back, this test will still consider that successful.

mikaey 1y ago
Absolutely a fair point, and that's something that I've thought about for a follow-up study.