Re: Patches for GPT and geli recovery

On 12/19/21 13:40, Lee Brown wrote:
> 
> 
> On Sun, Dec 19, 2021 at 8:52 AM Fabian Keil 
> <freebsd-listen@fabiankeil.de <mailto: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

How old was the corrupted filesystem?  I habitually wipe my disks and do 
a fresh install at least once every 2 years to avoid issues like this. 
I have experienced unexplained, unrecoverable errors on old filesystems, 
but fortunately nothing critical.

This to me serves as another reminder to maintain regular backups of 
important files and consider everything else expendable.

-- 
All wars are civil wars, because all men are brothers ... Each one owes
infinitely more to the human race than to the particular country in
which he was born.
                 -- Francois Fenelon