Re: Patches for GPT and geli recovery

On Sun, Dec 19, 2021 at 8:52 AM Fabian Keil <freebsd-listen@fabiankeil.de>
wrote:

> [cut]
> BTW, I would also be interested to know if others have
> experienced similar data corruption and could figure
> out how it happened.
>
Sounds like bitrot.  Bits flip on disks all the time, it doesn't matter if
they are spinning rust or SSD, it happens.  Sometimes they are detected and
corrected, in which case you won't know.  Sometimes they are detected and
uncorrectable, you'll see that error propagated into the driver.  And
sometimes they are not detected at all and cause no errors that the OS can
surmise.  The higher the density of bits, the higher the probability of
corruption.  SMART is not reliably predictive.  How does it happen?  Cosmic
rays and entropy.  I've had lighty written SSD's fail after a few months.

I don't use ZFS, but have GELI-Authentication under a GMIRROR, so whenever
a bad checksum is read, it breaks the mirror, which gets attention (Iast I
looked, there wasn't a simple userland hook for bad GELI reads, but there
was for GMIRROR add/remove events).

HTH - lee