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Date: Sun, 10 Mar 2013 10:22:41 -0600 (MDT)
From: Warren Block <wblock@wonkity.com>
To: Cody Ritts <cr@caltel.com>
Subject: Re: Aligning MBR for ZFS boot help
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On Sat, 9 Mar 2013, Cody Ritts wrote:

> Poking around on the internet, it looks like gpart is possibly enforcing 
> geometry boundaries?

Not gpart, but the kernel.  At present, I don't know of any way to use 
FreeBSD for creating MBR slices aligned to anything other than 63 
blocks.  FreeBSD partitions can be aligned inside a slice with an 
offset.  Putting ZFS on one of those partitions may be the easiest way 
to do this.  Put the slice at block 2016, then align the first FreeBSD 
partition inside that slice to 1M and it should land at block 2048.

Another option is to create the MBR with aligned slices using another 
operating system, one that allows deviation from the MBR standard. 
Ronald Guilmette recently showed an interesting approach of starting the 
slice at 63M, the least common multiple of 63 and 1M.

If the BIOS does not like GPT, check for BIOS updates.  And make sure 
the vendor knows about the problem.