New BSD Installer

[Freddie Cash]

If you're mirroring the disk with gmirror, how are you dual-booting the
disk?

This discussion is about using gmirror to mirror two entire disks, and then
use GPT to partition the mirror device.

Dual-booting has no bearing on that, as gmirror is a FreeBSD-only
technology.

Cheers,
Freddie Cash
fjwcash at gmail.com
On Feb 18, 2012 10:37 PM, "Kevin Oberman" <kob6558 at gmail.com> wrote:

> On Fri, Feb 17, 2012 at 1:50 PM, Freddie Cash <fjwcash at gmail.com> wrote:
> > On Fri, Feb 17, 2012 at 1:38 PM, Andriy Gapon <avg at freebsd.org> wrote:
> >> And just in case:
> >> Unified Extensible Firmware Interface Specification Version 2.3.1,
> Errata 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
> second
> >>> logical block), and the backup GPT Header must be located in the last
> LBA
> >>> of the device.
> >>
> >> I can not see any ambiguity or openness to interpretation in this
> paragraph.
> >
> > Unless it's specified somewhere else (which is possible), in this
> > paragraph, "device" does not necessarily mean "physical disk".  "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
> provides.
> >
> > After all, LBAs are logical addresses (it's right there in the name!),
> > not hardwired physical sector addresses.  ;)  If they were hardwired,
> > then how would internal sector remapping work?  ;)
>
> 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.
> --
> R. Kevin Oberman, Network Engineer
> E-mail: kob6558 at gmail.com
>