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Date:      Sat, 18 Feb 2012 22:37:03 -0800
From:      Kevin Oberman <kob6558@gmail.com>
To:        Freddie Cash <fjwcash@gmail.com>
Cc:        wblock@wonkity.com, mandrews@bit0.com, 000.fbsd@quip.cz, Andriy Gapon <avg@freebsd.org>, freebsd-stable@freebsd.org, freebsd@jdc.parodius.com
Subject:   Re: New BSD Installer
Message-ID:  <CAN6yY1skQ=eO39vvbE-mLFKZb5TxXJJqtWydZOQpVBsiZpBHYw@mail.gmail.com>
In-Reply-To: <CAOjFWZ5Jm9M27J=%2B2jj5b4mSyE_i1Jq2YyXBKs%2BPabrUQyiYhg@mail.gmail.com>
References:  <CAOjFWZ5EhGFr_Vp0%2BTRfxvgm6KZxv9QO3UfVdKurA96z3axDMQ@mail.gmail.com> <20120217.160430.406937514120319292.hrs@allbsd.org> <4F3E3000.9000206@FreeBSD.org> <20120217.232843.2212672671663755444.hrs@allbsd.org> <4F3EC8DD.6040500@FreeBSD.org> <CAOjFWZ5Jm9M27J=%2B2jj5b4mSyE_i1Jq2YyXBKs%2BPabrUQyiYhg@mail.gmail.com>

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On Fri, Feb 17, 2012 at 1:50 PM, Freddie Cash <fjwcash@gmail.com> wrote:
> On Fri, Feb 17, 2012 at 1:38 PM, Andriy Gapon <avg@freebsd.org> wrote:
>> And just in case:
>> Unified Extensible Firmware Interface Specification Version 2.3.1, Errat=
a A
>> September 7, 2011 says:
>> [snip]
>>> Two GPT Header structures are stored on the device: the primary and the
>>> backup. The primary GPT Header must be located in LBA 1 (i.e., the seco=
nd
>>> logical block), and the backup GPT Header must be located in the last L=
BA
>>> of the device.
>>
>> I can not see any ambiguity or openness to interpretation in this paragr=
aph.
>
> Unless it's specified somewhere else (which is possible), in this
> paragraph, "device" does not necessarily mean "physical disk". =A0"Last
> LBA of the device" could be interpreted as "last LBA of the GEOM
> provider".
>
> The beauty of GEOM is that "device" is whatever logical mapping it provid=
es.
>
> After all, LBAs are logical addresses (it's right there in the name!),
> not hardwired physical sector addresses. =A0;) =A0If they were hardwired,
> then how would internal sector remapping work? =A0;)

Please remember that some disks are dual-boot. FreeBSD may understand
geom has the backup one block from the last LBA on the disk, but no
other OS is likely to do so.

Unless I am missing something, this should be a non-starter. Totally
unacceptable. The backup belongs in the last and only in the last LBA
on the physical disk.
--=20
R. Kevin Oberman, Network Engineer
E-mail: kob6558@gmail.com



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