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Date:      Sat, 5 Feb 2005 20:18:29 -0600
From:      Karl Denninger <karl@denninger.net>
To:        hartzell@kestrel.alerce.com, freebsd-stable@freebsd.org, freebsd-geom@freebsd.org
Cc:        Pawel Jakub Dawidek <pjd@freebsd.org>
Subject:   Re: Problem with migrating onto a gmirror slice.
Message-ID:  <20050205201829.A14091@denninger.net>
In-Reply-To: <16901.26814.588055.457273@satchel.alerce.com>; from George Hartzell on Sat, Feb 05, 2005 at 04:45:50PM -0800
References:  <16901.26814.588055.457273@satchel.alerce.com>

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On Sat, Feb 05, 2005 at 04:45:50PM -0800, George Hartzell wrote:
> 
> I have a system that I set up to use a gmirror back in the 5.3beta
> days.  It's running fine but I don't remember exactly how I set it up.
> 
> It's a scsi system w/ two identical disks.
> 
> I'd like to migrate the installation to a new box that uses ide disks,
> and am basing my attempts on the
> 
>   "GEOM mirror Approach 2: Single Slice, Preferred, More Flexible"
> 
> portion of these instructions:
> 
>    http://people.freebsd.org/~rse/mirror/
> 
> Although the disk that I ended up with was bootable in the new system,
> I noticed that the slice table was messed up.  After a couple of
> tries, here's what I've found:
> 
> The machine is:
> 
>    FreeBSD merlin.alerce.com 5.3-RELEASE-p2 FreeBSD 5.3-RELEASE-p2 #9: Sat Dec 18 12:38:37 PST 2004     root@merlin.alerce.com:/usr/obj/usr/src/sys/MERLIN  i386
> 
> Here's the series of commands that I've performed to illustrate the
> problem:
> 
>    138  15:31   fdisk -v -B -I /dev/ad0
>    139  15:31   fdisk -s /dev/ad0
>    140  15:31   fdisk -s /dev/ad0 > ~hartzell/fdisk-initial
>    141  15:32   gmirror label -v -n -b round-robin disk0 /dev/ad0s1
>    142  15:32   fdisk -s /dev/ad0
>    143  15:32   bsdlabel -w -B mirror/disk0
>    144  15:32   bsdlabel -e mirror/disk0
>    145  15:33   fdisk -s /dev/ad0
>    146  15:34   fdisk -s /dev/ad0 > ~hartzell/fdisk-after
>    147  15:34   history
>    148  15:34   history > ~hartzell/history
> 
> After the fdisk at line 138, here's the slice table:
> 
>     /dev/ad0: 387621 cyl 16 hd 63 sec
>     Part        Start        Size Type Flags
>        1:          63   390721905 0xa5 0x80
> 
> The fdisk at line 142 showed that the slice table was fine after the
> gmirror step. 
> 
> But after the bsdlabels at lines 143 and 144 the slice table looks
> like this:
> 
>     /dev/ad0: 387621 cyl 16 hd 63 sec
>     Part        Start        Size Type Flags
>        4:           0       50000 0xa5 0x80
> 
> Here's the output of "bsdlabel /dev/mirror/disk0":
> 
>     # /dev/mirror/disk0:
>     8 partitions:
>     #        size   offset    fstype   [fsize bsize bps/cpg]
>       a:   524272       16    4.2BSD     2048 16384 32768 
>       b:  8336976   524288      swap                    
>       c: 390721904        0    unused        0     0         # "raw" part, don't edit
>       d:   524288  8861264    4.2BSD     2048 16384 32776 
>       e:   524288  9385552    4.2BSD     2048 16384 32776 
>       f: 380812064  9909840    4.2BSD     2048 16384 28552 
> 
> Anyone see what I'm missing?

This is how I've done it.

1. Use "sysinstall" to do the slice table on the new disk, writing the
   FreeBSD "Boot Manager".  QUIT Sysisntall after this (do NOT label the 
   slice)
2. gmirror label -b round-robin disk0 ad0s1
3. bsdlabel -e /dev/mirror/disk0
   Edit the label.  Subtract ONE from the "c" partition size, which will be
   one sector too long.  Write it out.  If you got it right, there should
   be no complaints on the write.  When you read it in, there should be
   only one (the "c") partition.
4. bsdlabel /dev/mirror/disk0 - insure that there are no complaints about
   the label.
5. newfs ....... each filesystem
6. Copy your filesystems over (use dump/restore, or pax)
7. Edit the /etc/fstab entries appropriately, make sure swapoff is in the
   /etc/rc file, etc.

The result should be bootable and run.

A bit different than the instructions in that page, but after fiddling with
it this is the procedure I came up with, and it works.

--
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