[linux-lvm] Recovering LVM configuration on crashed RAID partition

[linux-lvm] Recovering LVM configuration on crashed RAID partition

[Oliver Schembach]

Hi,

I'm running 4 IDE disks in my home server using software raid with the 
following partition layout:

hd[abcd]1   /boot (RAID 1)
hd[abcd]2   swap (RAID 5)
hd[abcd]3   / (RAID 5)
hd[abcd]4   (RAID 5) LVM with logical volumes /data and /business

Now hdb crashed and while trying to recover the root partition (before I 
replaced the faulty disk) I lost all data in the root partition 
(including the whole /etc directory tree). So after replacing the defect 
drive I installed a linux on hda3 (with swap partion on hda2) for 
recovering purposes. I actually left the LVM RAID partition untouched 
until I replaced the defect drive. After resyncing the new drive into 
the LVM partition I tried to get access to the data in the logical 
volumes, but without success. There are no PVs, no VGs, or LVs listed.

GPART did not give any positive results, but listed four primary 
partitions with all 00s in it:
* Warning: strange partition table magic 0x0000.
Primary partition(1)
   type: 000(0x00)(unused)
   size: 0mb #s(0) s(0-0)
   chs:  (0/0/0)-(0/0/0)d (0/0/0)-(0/0/0)r
   hex:  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00

Primary partition(2)
...

vgscan gives:
  Reading all physical volumes.  This may take a while...

pvscan gives:
  No matching physical volumes found

lvdisplay gives:
  No volume groups found

Since I didn't do anything with the LVM RAID partition the logical 
volumes and the data must still be there!!!

Is there any other way to get access to the LVM partitions?

Thanks in advance!

Oliver 

Re: [linux-lvm] Recovering LVM configuration on crashed RAID partition

[Oliver Schembach]

Karl O. Pinc schrieb:
>
> On 01/18/2006 08:13:12 AM, Oliver Schembach wrote:
>> Hi,
>>
>> I'm running 4 IDE disks in my home server using software raid with 
>> the following partition layout:
>>
>> hd[abcd]1   /boot (RAID 1)
>> hd[abcd]2   swap (RAID 5)
>
> I don't know what I'm doing with LVM so can't help, but I can
> say that you don't want to run swap on raid5.  Probably you
> want to run it on raid0, perhaps raid 1 if you've hot-swappable
> drives and want to maximize uptime.
>
> Karl <kop@meme.com>
> Free Software:  "You don't pay back, you pay forward."
>                  -- Robert A. Heinlein
>
>
>
Thanks for your recommendation regarding RAID 5 on swap partitions. 
There's not so much swapping on my machine, so I didn't really notice 
the drawbacks resulting from the CPU XORing for the raid 5 algarithm.  
My idea really was to avoid  the machine going down in case of a disk 
crash in the raid array.
But you are right, I will change the swap partition to RAID 1 (...if I 
ever will get back my data from my LVM partition...)

Regards,
    Oliver