Date: Thu, 28 Apr 2011 16:20:52 +0700 From: Edho P Arief <edhoprima@gmail.com> To: Daniel Kalchev <daniel@digsys.bg> Cc: freebsd-stable@freebsd.org Subject: Re: correct way to setup gmirror on 7.4? Message-ID: <BANLkTikUn5jRSDWmvpHV9nGuLyKT5KHg6A@mail.gmail.com> In-Reply-To: <4DB9303E.9090305@digsys.bg> References: <BANLkTimCFcw_Oyp9RmBhfCZ9-QORUQEwfA@mail.gmail.com> <xn0hddht75xo97q00a@news.gmane.org> <20110427221554.GB22139@lava.net> <BANLkTikDjPLijvWrpK4y48fp5q6c2LnpqA@mail.gmail.com> <4DB9303E.9090305@digsys.bg>
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On Thu, Apr 28, 2011 at 4:15 PM, Daniel Kalchev <daniel@digsys.bg> wrote: > > > On 28.04.11 01:30, Freddie Cash wrote: >> >> gmirror doesn't touch the start of the disk, but saves it's metadata >> in the last sector of the disk, and creates a new GEOM provider that's >> one sector shorter. >> >> GPT stores it's partition table in the first sector of the disk, and >> saves a backup copy of it in the last sector of the disk. > > This looks like layering issue to me. > > In theory, both gmirror and gpt should work on 'providers'. So if you give > an gmirrored provider to gpt it should touch the last sector of the gmirror, > but not the last sector of the disk - and not complain. It should not even > be able to see the last sector of the real disk. > > Is this hard to fix? > I believe it goes like this gmX: | gpt | data | gpt | which in actual disk goes like this: adY: | gpt | data | gpt | gmirror | so geom read gpt in the first sector but doesn't find it in the last sector.
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