On Sat, May 2, 2020 at 11:26 PM Zygo Blaxell <ce3g8jdj@xxxxxxxxxxxxxxxxxxxxx> wrote: > > On Sat, May 02, 2020 at 11:48:18AM -0600, Chris Murphy wrote: > > 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. > > Use dup metadata on all single-disk filesystems, unless you are making > an intentionally temporary filesystem (like a RAM disk, or a cache with > totally expendable contents). The correct function for maximizing btrfs > lifetime does not have "rotational" as a parameter. Btrfs defaults need to do the right thing. Currently it's single metadata for mkfs, and ssd mount option when sysfs reports the device rotational is false. This applies to eMMC and SD Cards. Whereas USB sticks report they're rotational for whatever reason, and in that case the default is DUP and nossd. But I don't know that rotational is the best way of assuming an allocator. -- Chris Murphy
