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Date:      Sat, 13 Jun 2009 22:23:29 -0700
From:      Marcel Moolenaar <xcllnt@mac.com>
To:        "James R. Van Artsdalen" <james-freebsd-current@jrv.org>
Cc:        Alexander Best <alexbestms@math.uni-muenster.de>, FreeBSD Current <freebsd-current@freebsd.org>
Subject:   Re: `gpart show` and secondary GPT header
Message-ID:  <ADAD4EA3-0D07-4CD5-8805-3D21BB40A5AD@mac.com>
In-Reply-To: <4A344C67.8000101@jrv.org>
References:  <permail-200906131853081e86ffa80000190b-a_best01@message-id.uni-muenster.de> <A7C988A9-DCFD-422B-B39D-B912FECEFD0D@mac.com> <4A344A9F.5020708@jrv.org> <BD2A6E6D-EC33-408E-913B-CAF96F774ACD@mac.com> <4A344C67.8000101@jrv.org>

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On Jun 13, 2009, at 6:03 PM, James R. Van Artsdalen wrote:

> Marcel Moolenaar wrote:
>>
>> On Jun 13, 2009, at 5:55 PM, James R. Van Artsdalen wrote:
>>
>>
>>> Jun 13 06:31:42 bigback kernel: GEOM: ad4: the secondary GPT table  
>>> is
>>> corrupt or invalid.
>>> Jun 13 06:31:42 bigback kernel: GEOM: ad4: using the primary only --
>>> recovery suggested.
>>> Jun 13 06:31:42 bigback kernel: GEOM: ad12: the secondary GPT  
>>> table is
>>> corrupt or invalid.
>>> Jun 13 06:31:42 bigback kernel: GEOM: ad12: using the primary only  
>>> --
>>> recovery suggested.
>>
>> Are you using gmirror by any chance?
>
> Partitions 2-6 use gmirror.

Ok. Unrelated then. When gmirror is used on the whole
disk, then it's possible that you get this error. The
problem is that there's no guarantee that gpart tastes
always before or always after gmirror. If you put gpart
on top of gmirror, then gpart sees a disk that's 1
sector smaller than the disk gmirror sees. If gpart
gets to taste before gmirror, it won't find the backup
header in the last sector, because it's where gmirror
puts its metadata.

Mirroring partitions does not have this problem...

-- 
Marcel Moolenaar
xcllnt@mac.com






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