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From: Mel <fbsd.questions@rachie.is-a-geek.net>
To: freebsd-questions@freebsd.org
Date: Tue, 28 Oct 2008 23:52:44 +0100
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Cc: Stefan Moro <stefan.moro@gmail.com>
Subject: Re: A gmirror question.
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On Tuesday 28 October 2008 17:53:20 Stefan Moro wrote:

> But if this is the case, how does gmirror know that it should use (in
> my example above) ad10 and not ad4 as the additional disk in the
> mirror.
> Or does gmirror use something else than the /dev entries to address disks??
>
> I'm just curious how gmirror does this.

It doesn't care about the device name. Geom modules that are loaded into the 
kernel, register a 'taste' function, with the geom(4) subsystem, that tastes 
if a provider is something they want to work with. Effectively, this taste 
function reads the last sector and checks if it has gmirror metadata.
The geom system is the 'magician', which basically hands all providers to the 
loaded modules.

-- 
Mel

Problem with today's modular software: they start with the modules
    and never get to the software part.