Booting from 3TB drive (UFS, BIOS)

[John Baldwin]

On Tuesday, August 14, 2012 9:23:19 am Oliver Fromme wrote:
> Hi,
> 
> I've got a small PC that currently has two disks:  The
> first one is 1 TB with a standard MBR, used to boot FreeBSD,
> and the second one is 3 TB with GPT, used as data disk for
> FreeBSD (the BIOS doesn't have to care about this one at all
> because it's not used for booting).
> 
> Now I would like to replace the first disk with a 3 TB one,
> too.  However, will I be able to boot from it?  The PC is
> not exactly a new one (ASRock A330GC with Atom 330 processor,
> a few years old) and has a standard BIOS (dated 07/16/2009).
> 
> I understand that I will have to use GPT in order to be able
> to use the full capacity of 3 TB, and that I will have to
> install a pmbr to enable the BIOS to detect the disk as
> bootable.  Is this correct?  Will that work?  (Assuming that
> the boot partition will have to be within the first 2 TB of
> the drive, of course.)
> 
> If everything else fails, I'd consider using an additional
> drive for booting, probably an SSD.  But I'd like to avoid
> this if possible.

A GPT boot should work, and the boot partition can even be
above 2 TB.  (GPT booting only uses the EDD BIOS interface
which uses 64-bit LBAs, and the GPT boot code will use all
64-bits of the LBAs stored in GPT, etc.)

-- 
John Baldwin