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Date: Thu, 12 Jul 2012 13:00:14 -0600 (MDT)
From: Warren Block <wblock@wonkity.com>
To: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>
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Cc: Kaya Saman <kayasaman@gmail.com>, miles kuo <miles.kuo@gmail.com>,
	freebsd-questions@freebsd.org
Subject: Re: How to mirror the FreeBSD OS on two disks
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On Thu, 12 Jul 2012, Wojciech Puchar wrote:

>>>> If that last block is already part of an MBR partition, the more strict 
>>>> checking stops booting in 9.0.
>>> 
>>> not making MBR partition would not make problems.
>> 
>> There's no guarantee that bsdlabel checking won't be made more strict. No 
>> matter what type of partitioning scheme, the metadata should not be
>> inside the data area.
>> 
> gmirror puts it's metadata at the end of disk.
> bsdlabel is at the beginning. what a problem?

It's not the label, it's what the label declares for the partitions.  If 
the last partition includes the block of gmirror metadata, that's an 
error.  Pardon the ASCII diagrams.

Wrong:

partition table

partition 1-------
|                 |
  -----------------

...

partition n-------
|                 |
|gmirror metadata |
  -----------------


Right:

partition table

partition 1-----
|               |
  ---------------

...

partition n-----
|               |
  ---------------

gmirror metadata
|               |
  ---------------