gmirror gm0 destroyed on shutdown; GPT corrupt

[Ivan Voras]

2009/6/30 Rick C. Petty <rick-freebsd2008 at kiwi-computer.com>:
> On Tue, Jun 30, 2009 at 02:37:55PM -0700, Marcel Moolenaar wrote:

> Both bar and baz should validate their metadata and it should be pretty
> apparent that one of them has a smaller size.  If the one that is smaller
> fits perfectly into the one that is bigger, the taste should pass to the
> latter first.

This is how it's currently done with "native" GEOM classes like
gmirror - if gmirror is put where it and something else can taste the
metadata, gmirror will decide by checking the size - usually +/- 1
sector. But we can't embed this logic into "foreign" classes like GPT.
GTP check the first sector (and the last sector for backup), while
gmirror checks the first sector, and GPT metadata (AFAIK) doesn't
contain media size.