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Date: Wed, 06 Jun 2012 14:25:37 +0400
From: "Andrey V. Elsukov" <ae@FreeBSD.org>
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To: Hiroki Sato <hrs@FreeBSD.org>
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Subject: Re: Handbook mirroring section
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On 06.06.2012 13:50, Hiroki Sato wrote:
>  Thanks, I will review the new version.
> 
>  BTW, do you (or anyone) know the common failure pattern when trying
>  to use GPT + gmirror of the whole disk?  

There was a warning from the gptboot about corrupted backup GPT header.
But now the behavior has changed with r234692 and later it has been
merged to stable. So, when you are doing all in the right way - it should work.

But:
1. When geom_mirror module is not loaded GEOM_PART will complain that the
backup GPT header is not in the last LBA and partition table will be marked
as CORRUPT. The recover operation will destroy the GEOM_MIRROR's metadata.

2. If primary GPT header or table become damaged, then gptboot will not
detect GPT because the backup GPT header is not in the last LBA. So, the
system will not boot.

-- 
WBR, Andrey V. Elsukov