gmirror - one provider won't activate

illoai at illoai at
Fri Apr 20 12:18:37 UTC 2007

On 19/04/07, Cam Baillie <cambaillie at> wrote:

> I set up a RAID 1 duplex following the well-laid out OnLamp
> article.  I had successfully synchronised both disks prior to
> rebooting.  Then I rebooted and the ad3 disk wouldn't activate.
> The system boots off of ad0 while slices within ad1 and ad3 are
> supposed to serve as the duplex.  The duplex (/dev/mirror/gm0)
> mounts successfully to /usr/home so I have access to my data
> from ad1.
> I am running 6.2-release.  The dmesg and fstab files are attached.

The pertinant lines from dmesg:
 ad0: 76319MB <Seagate ST380021A 3.10> at ata0-master UDMA100
 ad1: 286168MB <Seagate ST3300631A 3.04> at ata0-slave UDMA100
 acd0: CDRW <NEC CD-RW NR-7900A/1.08> at ata1-master UDMA33
 ad3: 286168MB <Seagate ST3300631A 3.04> at ata1-slave UDMA100
 GEOM_MIRROR: Device gm0 created (id=2536797825).
 GEOM_MIRROR: Device gm0: provider ad1 detected.
 GEOM_MIRROR: Device gm0: provider ad3 detected.
 GEOM_MIRROR: Component ad3 (device gm0) broken, skipping.
 GEOM_MIRROR: Device gm0: provider ad1 activated.
 GEOM_MIRROR: Device gm0: provider mirror/gm0 launched.

Distressingly, from searching google with the line:
GEOM_MIRROR: Component broken, skipping.
I find lots of references to disk failures.  Worse,
there are several unanswered posts with nearly
this very question.
The cause of the error seems to be metadata
corruption, which could be something as innocent
as cosmic rays, or the dying screams of a thoroughly
tormented hard-drive.

One suggestion was to try using something like:
# gmirror forget gm0
# gmirror insert gm0 /dev/ad3
And see if it works better.
I suppose the admonition to backup what data you
can from gm0 is not lost here.  Also, make sure that
all cables are properly seated.


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