8.2-RELEASE - gmirror and gpart issue. Metadata overlap?

[Clifton Royston]

On Mon, Feb 28, 2011 at 06:23:10PM +0200, Marin Atanasov Nikolov wrote:
> 2011/2/28 Andrey V. Elsukov <bu7cher at yandex.ru>:
> > On 28.02.2011 11:54, Johan Hendriks wrote:
> >> I opened a discussion on this before the release.
> >> http://lists.freebsd.org/pipermail/freebsd-stable/2011-January/061184.ht
> >> ml
> >> On my 8.1 system, i get this message about the corrupt headers, but it
> >> booted on the 8.2 system it panics...
> >>
> >> I think a lot of people are going to get bit by this.
> >>
> >> As far as i know there is no warning anywhere that you can not use gpart
> >> and gmirror the whole disk.
> >
> 
> I can confirm as well that I get kernel panic  if I gpart and then
> gmirror a disk on 8.2-RELEASE.
> 
> To reproduce it, I just did the following:
> 
> 1) Boot a system with a Fixit image
> 2) Remove all gpart partitions
> 3) gpart the first disk (ad0)
> 4) Restored my data to the partitions from backups
> 5) Reboot
> 6) gmirror the ad0 disk
> 
> And that's where I got kernel panic.
> 
> gpart'ing the disk and the mirroring the partitions works just as
> fine, but not when you mirror the whole disk.

  I think this only ever worked accidentally at best.  It would work
fine with the older fdisk-style disk partition because that doesn't
touch the end of the disk, but any time you tell two different programs
that they both have absolute control over the last sector on the disk
and can write critical data there - which is what this is doing -
that's begging for trouble.

  Something cleaner than a kernel panic would be *nice* however...  And
your point about warnings in the documentation is a good one.

  -- Clifton

-- 
    Clifton Royston  --  cliftonr at iandicomputing.com / cliftonr at lava.net
       President  - I and I Computing * http://www.iandicomputing.com/
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