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Date: Fri, 2 Oct 2015 17:06:41 -0600 (MDT)
From: Warren Block <wblock@wonkity.com>
To: "Chad J. Milios" <milios@ccsys.com>
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On Fri, 2 Oct 2015, Chad J. Milios wrote:

>> GPT does not work well with that.  If the target device is larger, the 
>> backup GPT that is supposed to go at the very end of the disk ends up 
>> someplace before that.  If the target device is smaller, well, it won't 
>> work at all.
>
> he's right. unless your md is exactly the correct total size, to the byte, 
> the backup GPT header will be lost after copying to a different device. alas, 
> it is a backup after all, unless/until the primary header suffers calamity, 
> it'll cause you no grief.

Well... due to kern.geom.part.check_integrity defaulting to 1, the 
system might refuse to boot.  Or it might just complain, I forget.