update to 8.0-RELEASE --> partition gone

[Marian Hettwer]

Hi Folks,

today I did an update from 7.2-RELEASE-p4 to 8.0-RELEASE using 
freebsd-update.
Everything went smooth, apart from the fact that I can't mount my second 
disk.
It's all a bit puzzling...
Here are the facts:

[root at talisker ~]# cat /etc/fstab       
# Device        Mountpoint    FStype    Options        Dump    Pass#
/dev/ad4s2b        none        swap    sw        O    O
/dev/ad4s1a        /        ufs    rw        1    1
/dev/ad4s2a        /tmp        ufs    rw        2    2
/dev/ad4s2d        /var        ufs    rw        2    2
/dev/ad4s2e        /usr        ufs    rw        2    2
/dev/ad8s1a        /BACKUP        ufs    rw        2    2
/dev/acd0        /cdrom        cd9660    ro,noauto    0    0
linproc        /compat/linux/proc    linprocfs    rw 0    0

The offending entry which isn't mountable anymore is ad8s1.
[root at talisker ~]# sysctl kern.disks
kern.disks: ad8 ad4

fdisk and bsdlabel are showing my s1a partition/slice:
[root at talisker ~]# fdisk ad8
******* Working on device /dev/ad8 *******
parameters extracted from in-core disklabel are:
cylinders=775221 heads=16 sectors/track=63 (1008 blks/cyl)

Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=775221 heads=16 sectors/track=63 (1008 blks/cyl)

Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 165 (0xa5),(FreeBSD/NetBSD/386BSD)
    start 63, size 781422705 (381554 Meg), flag 80 (active)
    beg: cyl 0/ head 1/ sector 1;
    end: cyl 52/ head 15/ sector 63
The data for partition 2 is:
<UNUSED>
The data for partition 3 is:
<UNUSED>
The data for partition 4 is:
<UNUSED>
[root at talisker ~]# bsdlabel ad8
# /dev/ad8:
8 partitions:
#        size   offset    fstype   [fsize bsize bps/cpg]
  a: 781422752       16    unused        0     0      
  c: 781422768        0    unused        0     0         # "raw" part, 
don't edit

but:
[root at talisker ~]# mount /dev/ad8s1a /BACKUP/
mount: /dev/ad8s1a : No such file or directory

And in fact:
[root at talisker ~]# ls -l /dev/ad8*
crw-r-----  1 root  operator    0,  91 Dec 15 17:58 /dev/ad8
crw-r-----  1 root  operator    0,  96 Dec 15 17:58 /dev/ad8a

Huu? What's going on here? Where is s1?
Never seen that before... (and I'm using FreeBSD since 4.0-RELEASE).
and this mount obviously won't work either:
[root at talisker ~]# mount /dev/ad8a /BACKUP/
mount: /dev/ad8a : Invalid argument

Anybody any idea how to recover here?
The server is unluckily remote and in production. A downgrade back to 
7.2 would be kinda difficult. I'd like to avoid that.

Ideas anyone?

Thanks in advance,
Marian

PS.:
dmesg: http://crivens.terrorteam.de/~rabauke/FreeBSD/dmesg-8.0-release.txt
[root at talisker ~]# uname -rms
FreeBSD 8.0-RELEASE i386