no file system for xbd0 (dev 0x8e00)

["Emile `iMil' Heitor" <imil%home.imil.net@localhost>]

Hi,

Since yesterday, a NetBSD 6.0.1/amd64 domU of mine can't mount its root fs
anymore:

boot device: xbd0
root on xbd0a dumps on xbd0b
Your machine does not initialize mem_clusters; sparse_dumps disabled
Supported file systems: union umap tmpfs smbfs puffs ptyfs procfs overlay null 
ntfs nfs msdos mfs lfs kernfs fdesc ext2fs ffs coda cd9660
no file system for xbd0 (dev 0x8e00)
cannot mount root, error = 79
root device (default xbd0a):

That domU used to boot / work peacefully, but for an unknown reason, the
virtual block device is not recognized anymore. When trying to mount that
device in another virtual machine, I get the following:

[~] mount -o log /dev/xbd1a /mnt
mount_ffs: /dev/xbd1a on /mnt: incorrect super block

Whereas disklabel indicates:

[~] disklabel /dev/xbd1
# /dev/xbd1d:
type: unknown
disk: Xen Virtual ESD
label: 
flags:
bytes/sector: 512
sectors/track: 2048
tracks/cylinder: 1
sectors/cylinder: 2048
cylinders: 20480
total sectors: 41943040
rpm: 3600
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0           # microseconds
track-to-track seek: 0  # microseconds
drivedata: 0

16 partitions:
#        size    offset     fstype [fsize bsize cpg/sgs]
 a:  37748736         0     4.2BSD   2048 16384     0  # (Cyl.      0 -  18431)
 b:   4194304  37748736       swap                     # (Cyl.  18432 -  20479)
 c:  41943040         0     unused      0     0        # (Cyl.      0 -  20479)
 d:  41943040         0     unused      0     0        # (Cyl.      0 -  20479)

The virtual block device is a LVM logical volume, I use that setup in almost
all of the domUs I run, it is declared very simply in domU's configuration
file:

disk = [ 'phy:/dev/mapper/vg1-webserver,hda,w' ]

Running fsck_ffs gives:

[~] fsck_ffs /dev/xbd1a 
** /dev/rxbd1a
BAD SUPER BLOCK: CAN'T FIND SUPERBLOCK
/dev/rxbd1a: CANNOT FIGURE OUT SECTORS PER CYLINDER

And specifying another superblock doesn't change anything:

[~] fsck_ffs -b 32 /dev/xbd1a 
Alternate super block location: 32
** /dev/rxbd1a
BAD SUPER BLOCK: MAGIC NUMBER WRONG

Any idea on what can I try in order to recover that virtual drive?

------------------------------------------------------------------
Emile `iMil' Heitor .°. <imil@{home.imil.net,NetBSD.org,gcu.info}>
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