9.0 beta2 & the new bsdinstaller

[Lucas Holt]

1MB is a magic number. It works with advanced format disks, traditional disks, some odd SSD and most raid configurations. 

Lucas Holt

On Sep 21, 2011, at 4:26 AM, "Thomas Mueller" <mueller6727 at bellsouth.net> wrote:

>> From "Matthew D. Fuller" <fullermd at over-yonder.net>:
> 
>> I've been meaning to mention this, but we really should document
>> somewhere that it has a _MAXIMUM_ size.
> 
>> I setup a system a few weeks back with GPT, and figured I'd just make
>> the first 'real' partition start at the 1 meg mark.  And make
>> everything before that (1 meg - the however many sectors for the pmbr)
>> the freebsd-boot partition.
> 
>> It worked fine, up 'till the point that I tried to boot, and it
>> completely failed to, complaining that the boot code was too big.  I
>> had to track around in pmbr to find
> 
>> .   .   cmp $0x9000,%ax..   .   # Don't load past 0x90000,
>> .   .   jae err_big..   .   #  545k should be enough for
>> .   .   mov %ax,%es..   .   #  any boot code. :)
> 
>> and redo the partition to 512k (leaving a few hundred k unused before
>> the next partition started) before it would boot.  That's a little
>> nerve-wracking to hit on a critical system...
> 
> I don't think there is any particular advantage in aligning GPT partitions on 1 MB boundaries.
> 
> Nothing sacred about being an integer power of 2, wouldn't it be sufficient for boot partition size to be divisible by 4096 bytes, when the hard drive sector size is 4096 bytes?
> 
> 
> Tom
> 
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