BIOS booting from disks > 2TB

Borja Marcos borjam at
Thu Nov 20 06:57:43 UTC 2014

On Nov 19, 2014, at 6:29 PM, Warren Block wrote:

> On Wed, 19 Nov 2014, José María Alcaide wrote:
>> On Nov 19, 2014, at 8:06 AM, Pokala, Ravi wrote:
>>> When you perform your installation, just make sure to select the GPT
>>> option for partitioning. The installer (either `bsdinstall' (for stock
>>> FreeBSD), or `pc-sysinstall' (for PC-BSD / FreeNAS)) should create both
>>> primary (near start-of-disk) and backup (at end-of-disk) GPT tables, and
>>> install the appropriate bootstrap code in the proper locations.
>> Yes, bsdinstall flawlessly creates both primary and backup GPT tables even using disks > 2 TB, by virtue of the FreeBSD kernel. The problem arises at the first stages of booting, when gptboot tries to compare the primary and backup tables *using the BIOS disk services*, which are not able to reach anything after the 2 TB limit. As a consequence gptboot fails, stating that it did not find the GPT backup table.
> Maybe kern.geom.part.check_integrity=0 will allow it to boot.  However, this sounds like a bug in gptboot.  Maybe not easy to fix, but increasingly important as disks > 2TB become common.

I did a manual install on a 3 TB disk, creating a small partition for the  OS, around 4 GB.

The booot sequence was:

Attempting Boot From Hard Drive (C:)
gptboot: invalid backup GPT header

BTX loader 1.00 BTW version is 1.02
Consoles: internal video/keyboard
BIOS drive C: is disk0
BIOS 614kB/3961744kB available memory

FreeBSD/x86 bootstrap loader, Revision 1.1
(root at
Can't work out which disk we are booting from.
Guessed BIOS device 0xffffffff not found by probes, defaulting to disk0:

can't load 'kernel'

And that's it. It would be nice indeed if FreeBSD could boot from >2TB disks on BIOS machines. What
I wonder is, is this just some brain dead bug in this machine (HP Proliant Microserver Gen8 with the latest
BIOS version) or a widespread problem?

It's not a pressing issue for myself, as anyway I intended to boot from a memstick and use the  disks
just for a ZFS pool, but anyone trying to set up a ZFS on root boot will run into problems.


More information about the freebsd-fs mailing list