Bug#534470: Using mdadm 2.6.7.2 to assemble a raid array created with mdadm 1.9.0 will corrupt it making mdadm 1.9.0 to crash when trying to reassemble

[RUSSOTTO François-Xavier 200103]

Dear Neil,

I am sorry for insisting:

It is NOT ONLY a problem for people migrating to newer kernel then going back to an old kernel. It is a problem for people that SIMPLY BOOT A CDROM with a newer distribution/kernel on an older distribution/kernel (which was my case). I did not want to upgrade my kernel at all. Simply booting the CDROM did corrupt my raid array with no prompt; I did not run any install/upgrade process.

Regards,

> -----Message d'origine-----
> De : Neil Brown [mailto:neilb at suse.de]
> Envoyé : jeudi 28 janvier 2010 01:28
> À : martin f krafft
> Cc : RUSSOTTO François-Xavier 200103; 534470 at bugs.debian.org
> Objet : Re: Bug#534470: Using mdadm 2.6.7.2 to assemble a raid array
> created with mdadm 1.9.0 will corrupt it making mdadm 1.9.0 to crash when
> trying to reassemble
> 
> On Wed, 27 Jan 2010 14:13:36 +1300
> martin f krafft <madduck at debian.org> wrote:
> 
> > also sprach RUSSOTTO François-Xavier 200103 <francois-
> xavier.russotto at cea.fr> [2009.12.02.0407 +1300]:
> > > As I suggested to Neil: prior to auto-remount a raid array, the
> > > raid tool should perform a version checking so that, at least,
> > > user is warned that the raid array might be corrupt performing
> > > such operation.
> >
> > Neil, does this sound like a feasible solution to
> > http://bugs.debian.org/534470?
> 
> I don't think so.
> We really want old arrays to work smoothly on new kernels.
> To avoid a repartition of the original problem we would need not just a
> message, but an option not to assemble the array and that would be awkward
> for
> people normally upgrading their system.
> 
> So I don't think there is a solution for this problem that does not
> introduce
> other problems.
> It does not affect x86 architectures, and is only a problem if you move to
> a
> new kernel, then back to an old kernel.  So hopefully it will be very
> rare.
> 
> Sorry.
> 
> NeilBrown