On Sat, May 2, 2020 at 3:09 AM Zygo Blaxell <ce3g8jdj@xxxxxxxxxxxxxxxxxxxxx> wrote: > > On SD/MMC and below-$50 SSDs, silent data corruption is the most common > failure mode. I don't think these disks are capable of detecting or > reporting individual sector errors. I've never seen it happen. They > either fall off the bus or they have a catastrophic failure and give > an error on every single access. I'm still curious about the allocator to use for this device class. SD Cards usually self-report rotational=0. Whereas USB sticks report rotational=1. The man page seems to suggest nossd or ssd_spread. In my very limited sample size from a single vendor, I've only seen SD Card fail by becoming read only. i.e. hardware read-only, with the kernel spewing sd/mmc related debugging info about the card (or card's firmware). Maybe that's a good example? I suppose it's better to go read-only with data still readable, and insofar as Btrfs was concerned the data was correct, rather than start returning transiently bad data. However, I only knew this due to data checksums. -- Chris Murphy
