gmirror gm0 destroyed on shutdown; GPT corrupt

Anton Shterenlikht mexas at
Mon Jun 29 09:39:03 UTC 2009

On Thu, Jun 25, 2009 at 09:41:13AM -0700, Marcel Moolenaar wrote:
> On Jun 25, 2009, at 4:02 AM, Anton Shterenlikht wrote:
> > dev_taste(DEV,mirror/gm0)
> > g_part_taste(PART,mirror/gm0)
> >
> > GEOM: mirror/gm0: the secondary GPT table is corrupt or invalid.
> > GEOM: mirror/gm0: using the primary only -- recovery suggested.
> > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> You created the mirror after the GPT, which means you destroyed
> the GPT backup header. gmirror uses the last sector on the disk
> for metadata and that by itself is a cause for various problems.

So, gmirror cannot be used on ia64 to mirror the boot disk?

Because on ia64 the last sector always contains secondary GPT.
I take it the RAID1 section, 19.4, in FBSD user manual,
was written with i386 or alpha architecture in mind.

> It's better to use gmirror per partition.

how? Is it in the manual? any link?

> > #echo 'geom_mirror_load="YES"' >> /boot/loader.conf
> Is /boot a symlink for /efi/boot?


lrwxr-xr-x   1 root  wheel         8 Jun 25 10:44 boot -> efi/boot

> > And when the system is rebooted, there is no /dev/mirror anymore.
> You could run into a race condition between GPT and gmirror and
> GPT winning (again the result of gmirror using the last sector
> on a disk for metadata).
> Alternatively, make sure gmirror got loaded at boot.

# kldstat
Id Refs Address            Size     Name
 1    3 0xe000000004000000 ff9c08   kernel
 2    1 0xe000000004ffa000 3c830    geom_mirror.ko

It's not that I desperately need to mirror a boot disk, it just that
gmirror looked so easy in the manual, I wanted to give it a go.

Perhaps I can just do a block copy to the second disk, say once a day,
and have it as a backup.

Could you also possibly comment on gvinum on ia64?

many thanks

Anton Shterenlikht
Room 2.6, Queen's Building
Mech Eng Dept
Bristol University
University Walk, Bristol BS8 1TR, UK
Tel: +44 (0)117 928 8233 
Fax: +44 (0)117 929 4423

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