One of 8 PVs dead - Trying to rescue data from remaining 7

Hi,
I know this is a long post, but please take the time to at least read this paragraph;

Summary: One of my 8 PVs is dead and I despirately need to rescue the data from the other 7, even if its just read-only is fine, as long as I can see it.

I don't have a backup, so I know this is my fault. Please have some sympathy and help me anyway :)

Details:

System:
Gentoo linux:
Linux vaus 2.6.11.10 #2 SMP Mon May 30 02:46:52 GMT 2005 i686 AMD Athlon(tm) Processor AuthenticAMD GNU/Linux

I have an 8 disk lvm array (linear, non-striped) The last disk in the array has died completely (head crash) so i've had to remove it from the system, but now of course, I can't see any of my volume group.

My 8 PVs make up 1 volume group called vg1, It consists of 1 logical volume, called lv1, which contains ext2.

The lvm array was originally built back when I was using kernel 2.4.18 with LVM1. Now im using LVM2 & device mapper - but I havent changed anything, It just worked since I rebuilt the system.

The dead disk was the last one added to the array and contains nothing, I noticed it went wrong when I heard a loud clicking noise from the 8th PV when copying a file onto the vg that took it over the boundary to the 8th PV.

I'm absolutely despirate, so I'm really hoping there is a way to at least see the data on the 7 remaining PVs. All the disks are 100% ok and it's not striped so the data should be intact.

I've trawled the web and found 2 possible solutions:
*1: Do a partial read only mount of the VG.
This did not work - see below...

vaus root # vgchange -P -a y vg1
Partial mode. Incomplete volume groups will be activated read-only. 7 PV(s) found for VG vg1: expected 8
Logical volume (lv1) contains an incomplete mapping table. 7 PV(s) found for VG vg1: expected 8
Logical volume (lv1) contains an incomplete mapping table. 1 logical volume(s) in volume group "vg1" now active

vaus root # ls -l /dev/mapper/ total 0
crw-rw---- 1 root root 10, 63 May 30 02:48 control brw------- 1 root root 254, 0 Oct 25 13:20 vg1-lv1

vaus root # mount /dev/mapper/vg1-lv1 /mnt/test/
mount: you must specify the filesystem type

vaus root # mount /dev/mapper/vg1-lv1 /mnt/test/ -t ext2
mount: wrong fs type, bad option, bad superblock on /dev/mapper/vg1-lv1,
or too many mounted file systems
(could this be the IDE device where you in fact use ide-scsi so that sr0 or sda or so is needed?)

Something seems to be wrong with the vg1-lv1 block device, any ideas?

*2: Put a new disk in and write the uuid of the dead disk onto it. The problem here is I can't find anyway of getting the old UUID. I've grepped all the logs in /var/log and /etc/lvm and cant find anything. Interestingly the backup stuff just shows 7 PVs too, I think it's only backing up the last reboot.
Anyway, I heard that doing:

pvdata -U

Will retrieve the UUIDs of all the PVs from anyt working drive, but it's an LVM1 command, and now i'm running 2.6 with LVM2/device mapper and I cannot build the lvm tools (at least i dont seem to be able to).

Is there any way I can get this info without building an LVM1 system?

It was built on LVM1, the UUIDs must be stored on each drive.

Thanks in advance for any help,
I know this is my problem, but when I lost this data my world colapsed! I would be very appreciative of any information.

Below are some outputs of various commands. If you need any more information I would be happy to give it.
Any suggestions I can try out right away and get back to you.

Kind regards,
Tom Robinson

vaus root # pvscan
7 PV(s) found for VG vg1: expected 8
Logical volume (lv1) contains an incomplete mapping table.

 PV /dev/hda     VG vg1   lvm1 [233.72 GB / 0    free]
 PV /dev/hdc     VG vg1   lvm1 [233.72 GB / 0    free]
 PV /dev/cdrom   VG vg1   lvm1 [152.62 GB / 0    free]
 PV /dev/hde4    VG vg1   lvm1 [109.56 GB / 0    free]
 PV /dev/hdb     VG vg1   lvm1 [233.72 GB / 0    free]
 PV /dev/hdf     VG vg1   lvm1 [114.44 GB / 0    free]
 PV /dev/hdh     VG vg1   lvm1 [233.72 GB / 0    free]

Total: 7 [1.28 TB] / in use: 7 [1.28 TB] / in no VG: 0 [0 ]

* The dead disk was a 250G - all disks are maxtors, normal size of VG is 1.51TB (1690 hard disk gigs)

vaus root # vgchange -a y vg1
7 PV(s) found for VG vg1: expected 8
7 PV(s) found for VG vg1: expected 8
Unable to find volume group "vg1"

vaus root # vgdisplay -v
Finding all volume groups
Finding volume group "vg1"
Wiping cache of LVM-capable devices
7 PV(s) found for VG vg1: expected 8
7 PV(s) found for VG vg1: expected 8
Volume group "vg1" doesn't exist

vaus root # pvdisplay -v
Scanning for physical volume names
Wiping cache of LVM-capable devices
7 PV(s) found for VG vg1: expected 8
Logical volume (lv1) contains an incomplete mapping table. --- Physical volume ---

 PV Name               /dev/hda
 VG Name               vg1
 PV Size               233.76 GB / not usable 44.44 MB
 Allocatable           yes (but full)
 PE Size (KByte)       32768
 Total PE              7479
 Free PE               0
 Allocated PE          7479
 PV UUID               ofE07R-sevF-QJp0-xJ2k-Ga3z-fkIW-SDsS3F

--- Physical volume ---

 PV Name               /dev/hdc
 VG Name               vg1
 PV Size               233.76 GB / not usable 44.44 MB
 Allocatable           yes (but full)
 PE Size (KByte)       32768
 Total PE              7479
 Free PE               0
 Allocated PE          7479
 PV UUID               K8CRuK-5ybE-1GPS-qxXY-cybH-asIa-KKkZmt

--- Physical volume ---

 PV Name               /dev/cdrom
 VG Name               vg1
 PV Size               152.67 GB / not usable 46.50 MB
 Allocatable           yes (but full)
 PE Size (KByte)       32768
 Total PE              4884
 Free PE               0
 Allocated PE          4884
 PV UUID               sKlDWY-DYK1-44tN-dfVU-qoaF-BKmX-wI3cAV

--- Physical volume ---

 PV Name               /dev/hde4
 VG Name               vg1
 PV Size               109.61 GB / not usable 51.21 MB
 Allocatable           yes (but full)
 PE Size (KByte)       32768
 Total PE              3506
 Free PE               0
 Allocated PE          3506
 PV UUID               efBrIF-U1AF-WeWs-7CCC-hQqg-JGh3-fT7IQt

--- Physical volume ---

 PV Name               /dev/hdb
 VG Name               vg1
 PV Size               233.76 GB / not usable 44.44 MB
 Allocatable           yes (but full)
 PE Size (KByte)       32768
 Total PE              7479
 Free PE               0
 Allocated PE          7479
 PV UUID               iG7W2l-oHuD-0VNl-L68d-aE9M-VSC1-oWnZM9

--- Physical volume ---

 PV Name               /dev/hdf
 VG Name               vg1
 PV Size               114.50 GB / not usable 62.94 MB
 Allocatable           yes (but full)
 PE Size (KByte)       32768
 Total PE              3662
 Free PE               0
 Allocated PE          3662
 PV UUID               16cN09-WSFr-B6nx-ybol-GlfM-07jY-5cRcfx

--- Physical volume ---

 PV Name               /dev/hdh
 VG Name               vg1
 PV Size               233.76 GB / not usable 44.44 MB
 Allocatable           yes (but full)
 PE Size (KByte)       32768
 Total PE              7479
 Free PE               0
 Allocated PE          7479
 PV UUID               lHJQbC-9wQv-ZAC9-w95D-dlE9-ITa7-QK6KrN

Tom, did you ever get this figured out? (I don't see any responses on the mailing list.) If so what did you do?

I am curious about what to do in general if I have one disc fail on a multi-LVM system. Personally I have a two disc LVM system. You problem made me realize I have no idea what to do to recover data if one of the discs has a problem. Anyone have the answer?

Craig

I use raid 5 just for this problem. Have dropped 2 of the 3 raid devices and system keeps on truckin'. You can hot add devices back in and keep going while they sync. Good luck.

-------------------
Regards,

Old Fart

Yeah, this would work with 3 discs, but doesn't answer the general question about recovering data from a single LVM drive. In my 2 drive system it wouldn't work. Any other ideas? I would assume that if one drive failed it should be trivial to be able to access the information on the remaining drive. If not, then I would be a lot safer going back to a non-LVM system using the two drives as distinct partitions.

Craig

Take a look at a 2 disk raid 1 array as a pv. I have seen that array degrade to 1 drive and the LV was ok.

Regards,

Old Fart

I think his question is not "how do I avoid data loss with multiple disks under LVM?" but more like "I lost a disk and had no redundancy, my LV was spread onto that disk, how do I recover the parts of it that are on the good disk(s)?"

However I've personally got no idea since I do everything to avoid ever being in that position and luckily have not been there yet.

Certainly I would never consider putting an LV on a disk with no redundancy these days but that's not what the OP is asking.

Andy