BIOS booting from disks > 2TB

Warren Block wblock at
Wed Nov 19 17:29:28 UTC 2014

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.

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