Re: geom_mirror silently upgrading metadata [Was: cvs commit: src UPDATING]

From: Peter Jeremy <peterjeremy_at_optushome.com.au>
Date: Tue, 15 Jul 2008 19:51:39 +1000
On 2008-Jul-15 02:14:46 -0700, Maxim Sobolev <sobomax_at_freebsd.org> wrote:
>Not really relevant to the change in question, but I think that the 
>whole idea of geom_mirror updating on-disk metadata automagically is not 
>  very well thought out. For example one could try booting 7.x kernel on 
>6.x system just to see how well it goes with the intention to revert 
>back if it doesn't work out well.

Agreed.  I raised the same issue on -stable in late June.

>and re-creating/re-syncing the mirror after that. I've run into exactly 
>this issue today, with the target machine stuck in unbootable state on 
>another continent many thousand miles away.

I was lucky that I didn't need to revert.

>IMHO metadata update should be performed if and only if explicitly 
>requested by the administrator.

Agreed.  It's especially worrying that there's absolutely no warning
that a particular version of geom_mirror has a different metadata
format and loading it will make your gmirror unusable with an older
gmirror.  IMHO, any geom changes changes that prevent reversion
should be noted in UPDATING (at the very least).

-- 
Peter Jeremy
Please excuse any delays as the result of my ISP's inability to implement
an MTA that is either RFC2821-compliant or matches their claimed behaviour.

Received on Tue Jul 15 2008 - 22:45:33 UTC

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