RFC: Project geom-events

[perryh at pluto.rain.com]

Lev Serebryakov <lev at freebsd.org> wrote:

>   GPT (and MBR) metadata placement is dictated from outside world,
> where is no GEOM and geom_label. They INTENDED to be used on DISKS.
> BIOSes should be able to find it :)

Certainly GPT and MBR must place an instance of the partition table
where the BIOS expects it, but there's no immediately obvious reason
why they must regard that instance as their GEOM metadata.  GPT puts
a second copy in the provider's last block, and AFAICT it could just
as well use _that_ instance -- or even a differently-formatted block
that included the same data -- as the primary.  MBR could do likewise.