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Re: [linux-lvm] f*cked up metadata on 1of3 LVM-disks



BigMac,

Okay, I think I have a solution, but it's your data, so beware.

First force the VG to activated.  To do this, use the -P flag (partial).  It will activate as much of the VG as it can find.  So, first:

vgscan -P
vgchange -ay -P vgdata

Then, get a backup of the metadata:

vgcfgbackup -f vgdata.lvm -P vgdata

Now, recreate the PV metadata on the damaged disk, just to get the UUID back:

pvcreate -ff -u 9kpWwu-LdwT-YiqV-DRPg-kSAN-plYN-v1Eq81 /dev/hdc

Now you should have the pv there but with inconsistent metadata.  Now, restore the metadata from the backup we just made:

vgcfgrestore -f vgdata.lvm vgdata

If the planets are aligned and you are very lucky, you might have your LV back.  Good luck, and I'm curious if this will actually work.

On May 21, 2007, at 8:57 AM, Dave Wysochanski wrote:

On Mon, 2007-05-21 at 12:38 +0200, BigMac wrote:
Nobody an idea how to recover the lvm meta data on the disk?
The data itself an the other disks are fine, just the first sectors of
/dev/hdc are gone by installing grub on it.

I had a deeper look on the disk with one of those low level disk editors
and there are still parts of the meta-data stored on the disk.
It seems to be that grub messed up just the first 17 sectors of the disk.

Regards,

BigMac


I am working on a tool to do recovery and pull metadata out of the
disks.  Maybe this will help you.  

You can try "pvck -v" in the latest upstream LVM code.  It does not
extract metadata to a file yet but makes an attempt at identifying areas
on the disk that contain metadata and prints the offsets and lengths
(you can then just dd to a file).  Since you have other PVs that are
valid you could at least get the latest metadata off one of those, then
use vgcfgrestore with this file and uuid option.

Also, can you send me the first 256K?  Something like:
dd if=/dev/hdc of=/tmp/file.raw bs=1024 count=256 and send
me /tmp/file.raw in an email attachment?

Maybe I can enhance the extraction and/or add this case to my unit test.
Ideas on enhancements welcome.  





BigMac schrieb:
Hi lists!

My fileserver stored it's data on 3 physical disks,building a
volumegroup with lvm2.
The mashine was running ubuntu dapper drake for a long time without any
problems but I decided to switch to ubuntu feisty fawn. Switching from
debian to dapper drake I installed and removed quite a lot of packages,
leaving a messy system, so I thought a new and clean installation with
feisty fawn might be a great idea.

box config with dapper drake:

hda: 120GB (PATA) systemdisk
hdb: unused
hdc: 250GB (PATA) part of the LVM-array
hdd: 250GB (PATA) part of the LVM-array
sda: 400GB (SATA) part of the LVM-array
sdb: DVD-RW (PATA on additional PCI-controller UDMA-100)

The additional IDE-controller was installed to be able to install even
more disks, but as I won't buy any new PATA stuff the controller was
dispensable.

new box config:

hda: 120GB (PATA) systemdisk
hdb: DVD-RW
hdc: 250GB (PATA) part of the LVM-array
hdd: 250GB (PATA) part of the LVM-array
sda: 400GB (SATA) part of the LVM-array

I exported the vg before shutting down dapper drake and while installing
festy fawn to the box I - no idea what did me do so - installed grub to
hdc. Ooops, this disk was part of the LVM array and so grub f*cked up
the lvm meta-data on hdc.

After installing grub to hda the box is running fine, despite the LVM
which can't find one of the vgs volumes:

Code:

bigmac knecht:~$ sudo pvscan
Couldn't find device with uuid '9kpWwu-LdwT-YiqV-DRPg-kSAN-plYN-v1Eq81'.
Couldn't find device with uuid '9kpWwu-LdwT-YiqV-DRPg-kSAN-plYN-v1Eq81'.
Couldn't find device with uuid '9kpWwu-LdwT-YiqV-DRPg-kSAN-plYN-v1Eq81'.
Couldn't find device with uuid '9kpWwu-LdwT-YiqV-DRPg-kSAN-plYN-v1Eq81'.
PV /dev/hdd         VG vgdata   lvm2 [232.88 GB / 0    free]
PV unknown device   VG vgdata   lvm2 [232.88 GB / 0    free]
PV /dev/sda         VG vgdata   lvm2 [372.61 GB / 4.00 MB free]
Total: 3 [838.38 GB] / in use: 3 [838.38 GB] / in no VG: 0 [0   ]

bigmac knecht:~$ sudo pvdisplay
Couldn't find device with uuid '9kpWwu-LdwT-YiqV-DRPg-kSAN-plYN-v1Eq81'.
Couldn't find device with uuid '9kpWwu-LdwT-YiqV-DRPg-kSAN-plYN-v1Eq81'.
Couldn't find device with uuid '9kpWwu-LdwT-YiqV-DRPg-kSAN-plYN-v1Eq81'.
Couldn't find device with uuid '9kpWwu-LdwT-YiqV-DRPg-kSAN-plYN-v1Eq81'.
--- Physical volume ---
PV Name               /dev/hdd
VG Name               vgdata
PV Size               232.88 GB / not usable 0
Allocatable           yes (but full)
PE Size (KByte)       4096
Total PE              59618
Free PE               0
Allocated PE          59618
PV UUID               locW5S-HNFK-b1WW-iOLt-olHl-2SNd-fmXKC8

--- Physical volume ---
PV Name               unknown device
VG Name               vgdata
PV Size               232.88 GB / not usable 0
Allocatable           yes (but full)
PE Size (KByte)       4096
Total PE              59618
Free PE               0
Allocated PE          59618
PV UUID               9kpWwu-LdwT-YiqV-DRPg-kSAN-plYN-v1Eq81

--- Physical volume ---
PV Name               /dev/sda
VG Name               vgdata
PV Size               372.61 GB / not usable 0
Allocatable           yes
PE Size (KByte)       4096
Total PE              95388
Free PE               1
Allocated PE          95387
PV UUID               YUJcsF-3XP7-OrbO-pITp-5z96-gw1A-DI11QS


bigmac knecht:~$ sudo vgscan
Reading all physical volumes.  This may take a while...
Couldn't find device with uuid '9kpWwu-LdwT-YiqV-DRPg-kSAN-plYN-v1Eq81'.
Couldn't find all physical volumes for volume group vgdata.
Couldn't find device with uuid '9kpWwu-LdwT-YiqV-DRPg-kSAN-plYN-v1Eq81'.
Couldn't find all physical volumes for volume group vgdata.
Couldn't find device with uuid '9kpWwu-LdwT-YiqV-DRPg-kSAN-plYN-v1Eq81'.
Couldn't find all physical volumes for volume group vgdata.
Couldn't find device with uuid '9kpWwu-LdwT-YiqV-DRPg-kSAN-plYN-v1Eq81'.
Couldn't find all physical volumes for volume group vgdata.
Volume group "vgdata" not found

I tried multiple Live-CDs like gparted (with testdisk), Ultimate Boot-CD
and SystemRescueCd, but none could help.

Any idea what to do to get the lvm up and running?
How to restore the metadata on hdc?

Best Regards,

BigMac

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-- 
Jayson Vantuyl
Systems Architect



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