Confusing smartd messages

[Rodney W. Grimes]

> On 2018-Jul-04 18:05:56 -0700, "Rodney W. Grimes" <freebsd-rwg at pdx.rh.CN85.dnsmgr.net> wrote:
> >It would be really nice if we had a way to tell ZFS to
> >do the equivelent of:
> >	dd if=/dev/ada1 of=/dev/ada1 bs=128k conv=noerror,sync
> >in some type of lowlevel scrub operation, with proper locking
> >which could easily repair most of these Pending Sector errors,
> 
> Agreed.
> 
> >It would of also been nice if the ata standard would of made a way
> >to get the LBA of pending sectors so that a very quick rewrite attempt
> >could be done to fix them.  IIRC this info is avalible, but in a vendor
> >specific way.
> 
> As a workaround, 
>   dd if=/dev/ada1 of=/dev/null bs=128k conv=noerro
> will report any errors.  You can then write zeroes or garbage to those
> sectors (optionally followed by a scrub if you overwrote more than the
> faulty sectors)

Though this is a good test to run be-aware that this
only report errors if infact the read fails,
and often pending sectors do not fail as they are a transient error.

This is also a very long and slow test, I can go to a PC3000
driver recovery based system and have the pending sector list
in a mater of a single command and less than 1s of time.

I can also some times obtain that info by hooking up a TTL
serial cable to the jumpers on the drive and issuing commands
to the controller chip.  But again, this is a very vendor
specific situation and rather intrusive to do.

-- 
Rod Grimes                                                 rgrimes at freebsd.org