[linux-lvm] rescue data after hd crash

[linux-lvm] rescue data after hd crash

[chris]

hi!

I have create a volume group with 4 250GByte harddisks with an ext3 file  
system.

now the third harddisk failed and the volume group is "dead", obviously.

lvscan tells me:
   Couldn't find device with uuid 'A57CS6-SFlw-1ROR-uIvO-cX2o-OE2g-N3SVZN'.
   Couldn't find all physical volumes for volume group media_volgrp.

in my understanding many of the files are still intact (those on the first  
two disks), and I would like to rescue these files.

i found no hints about such a crash recovery.
(checked http://www.tldp.org/HOWTO/LVM-HOWTO/)

my approach would be to "fake" the third disk, as see what the filesystem  
makes out of it.

any help is welcome.

cheers, chris

[linux-lvm] rescue data after hd crash

[chris]

hi all!

sorry if this is a double post, but i think the first post didn't succeed  
due to some registration race condition.

so here's my problem:

I have create a volume group with 4 250GByte harddisks with an ext3 file  
system on the 1TB result.

now the third harddisk failed and the volume group is "dead" - obviously.

lvscan tells me (like any other lv*, pv* command):
   Couldn't find device with uuid 'A57CS6-SFlw-1ROR-uIvO-cX2o-OE2g-N3SVZN'.
   Couldn't find all physical volumes for volume group media_volgrp.

in my understanding many of the files should still be intact (those on the  
first two disks), and I would like to rescue these files.

i found no hints about such a crash recovery.
(checked http://www.tldp.org/HOWTO/LVM-HOWTO/)

my approach would be to "fake" the third disk, as see what the filesystem  
makes out of it.

any help is welcome.

thanks, chris

Re: [linux-lvm] rescue data after hd crash

[Graham Wood]

On Wed, May 31, 2006 at 02:34:04PM +0200, chris wrote:
> I have create a volume group with 4 250GByte harddisks with an ext3 file  
> system on the 1TB result.
Stripe or concat?

> now the third harddisk failed and the volume group is "dead" - obviously.
The way you created the volume had no redundancy - therefore 25% of your data is gone, as 
well as the volume's "completeness".

If you did a concat, then you (with playing) may be able to get some data back from the 
first 500GB of the volume - but I wouldn't want to rely on anything that came back from it.  
I'd suggest getting hold of 2 identical blank disks, and doing a binary (dd) copy of disks 1 
and 2 to them - and then work on them.  You might be able to use vgcfg{backup,restore} to 
tell the system that this volume is actually only on 2 disks....  However, anything that 
references data > 500GB into the volume is almost definitely lost - because although you've 
got 750G-1TB, it's almost all going to be linked back into the section that you've lost.

If you did a stripe, then you can forget getting any data back off it.  You've lost every 
4th block of whatever size you striped on.  E.g. with a 64k stripe size, you'll have lost 
from 128k-192k, 384k-448k, etc. - and there's almost definitely going to be nothing 
salvagable from that.

Graham

Re: [linux-lvm] rescue data after hd crash

[Heinz Mauelshagen]

vgchange -ay --partial

On Wed, May 31, 2006 at 01:45:46PM +0100, Graham Wood wrote:
> On Wed, May 31, 2006 at 02:34:04PM +0200, chris wrote:
> > I have create a volume group with 4 250GByte harddisks with an ext3 file  
> > system on the 1TB result.
> Stripe or concat?
> 
> > now the third harddisk failed and the volume group is "dead" - obviously.
> The way you created the volume had no redundancy - therefore 25% of your data is gone, as 
> well as the volume's "completeness".
> 
> If you did a concat, then you (with playing) may be able to get some data back from the 
> first 500GB of the volume - but I wouldn't want to rely on anything that came back from it.  
> I'd suggest getting hold of 2 identical blank disks, and doing a binary (dd) copy of disks 1 
> and 2 to them - and then work on them.  You might be able to use vgcfg{backup,restore} to 
> tell the system that this volume is actually only on 2 disks....  However, anything that 
> references data > 500GB into the volume is almost definitely lost - because although you've 
> got 750G-1TB, it's almost all going to be linked back into the section that you've lost.
> 
> If you did a stripe, then you can forget getting any data back off it.  You've lost every 
> 4th block of whatever size you striped on.  E.g. with a 64k stripe size, you'll have lost 
> from 128k-192k, 384k-448k, etc. - and there's almost definitely going to be nothing 
> salvagable from that.
> 
> Graham
> 
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

-- 

Regards,
Heinz    -- The LVM Guy --

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Heinz Mauelshagen                                 Red Hat GmbH
Consulting Development Engineer                   Am Sonnenhang 11
Storage Development                               56242 Marienrachdorf
                                                  Germany
Mauelshagen@RedHat.com                            PHONE +49  171 7803392
                                                  FAX   +49 2626 924446
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Re: [linux-lvm] rescue data after hd crash

[chris]

Thanks Heinz,

this looks like what i was serching for. still, it didn't work out.

the first call of this command issued (apart from multiple "couln't find  
device..")
"device-mapper ioctl cmd 9 failed: Das Argument ist ung�ltig"
  (i hate german error messages, who invented this? it says "illegal  
argument")

but also "1 logic voliume(s) .. now active".

lvscan says "Volume group ... not found"
mount fails.

what should i try next?

regards, Chris

PS: about the stripes, I don't think I have any.

On Wed, 31 May 2006 23:31:54 +0200, Heinz Mauelshagen  
<mauelshagen@redhat.com> wrote:

>
> vgchange -ay --partial
>
> On Wed, May 31, 2006 at 01:45:46PM +0100, Graham Wood wrote:
>> On Wed, May 31, 2006 at 02:34:04PM +0200, chris wrote:
>> > I have create a volume group with 4 250GByte harddisks with an ext3  
>> file
>> > system on the 1TB result.
>> Stripe or concat?
>>
>> > now the third harddisk failed and the volume group is "dead" -  
>> obviously.
>> The way you created the volume had no redundancy - therefore 25% of  
>> your data is gone, as
>> well as the volume's "completeness".
>>
>> If you did a concat, then you (with playing) may be able to get some  
>> data back from the
>> first 500GB of the volume - but I wouldn't want to rely on anything  
>> that came back from it.
>> I'd suggest getting hold of 2 identical blank disks, and doing a binary  
>> (dd) copy of disks 1
>> and 2 to them - and then work on them.  You might be able to use  
>> vgcfg{backup,restore} to
>> tell the system that this volume is actually only on 2 disks....   
>> However, anything that
>> references data > 500GB into the volume is almost definitely lost -  
>> because although you've
>> got 750G-1TB, it's almost all going to be linked back into the section  
>> that you've lost.
>>
>> If you did a stripe, then you can forget getting any data back off it.   
>> You've lost every
>> 4th block of whatever size you striped on.  E.g. with a 64k stripe  
>> size, you'll have lost
>> from 128k-192k, 384k-448k, etc. - and there's almost definitely going  
>> to be nothing
>> salvagable from that.
>>
>> Graham
>>
>> _______________________________________________
>> linux-lvm mailing list
>> linux-lvm@redhat.com
>> https://www.redhat.com/mailman/listinfo/linux-lvm
>> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>

Re: [linux-lvm] rescue data after hd crash

[Heinz Mauelshagen]

On Thu, Jun 01, 2006 at 12:39:39AM +0200, chris wrote:
> Thanks Heinz,
> 
> this looks like what i was serching for. still, it didn't work out.
> 
> the first call of this command issued (apart from multiple "couln't find  
> device..")
> "device-mapper ioctl cmd 9 failed: Das Argument ist ung�ltig"
>  (i hate german error messages, who invented this? it says "illegal  
> argument")
> 
> but also "1 logic voliume(s) .. now active".

Well, looks like your Logical Volume got activated.
Of course with a hole punched out (the missing drive).

Try to mount it manually.

Heinz

> 
> lvscan says "Volume group ... not found"
> mount fails.
> 
> what should i try next?
> 
> regards, Chris
> 
> PS: about the stripes, I don't think I have any.
> 
> On Wed, 31 May 2006 23:31:54 +0200, Heinz Mauelshagen  
> <mauelshagen@redhat.com> wrote:
> 
> >
> >vgchange -ay --partial
> >
> >On Wed, May 31, 2006 at 01:45:46PM +0100, Graham Wood wrote:
> >>On Wed, May 31, 2006 at 02:34:04PM +0200, chris wrote:
> >>> I have create a volume group with 4 250GByte harddisks with an ext3  
> >>file
> >>> system on the 1TB result.
> >>Stripe or concat?
> >>
> >>> now the third harddisk failed and the volume group is "dead" -  
> >>obviously.
> >>The way you created the volume had no redundancy - therefore 25% of  
> >>your data is gone, as
> >>well as the volume's "completeness".
> >>
> >>If you did a concat, then you (with playing) may be able to get some  
> >>data back from the
> >>first 500GB of the volume - but I wouldn't want to rely on anything  
> >>that came back from it.
> >>I'd suggest getting hold of 2 identical blank disks, and doing a binary  
> >>(dd) copy of disks 1
> >>and 2 to them - and then work on them.  You might be able to use  
> >>vgcfg{backup,restore} to
> >>tell the system that this volume is actually only on 2 disks....   
> >>However, anything that
> >>references data > 500GB into the volume is almost definitely lost -  
> >>because although you've
> >>got 750G-1TB, it's almost all going to be linked back into the section  
> >>that you've lost.
> >>
> >>If you did a stripe, then you can forget getting any data back off it.   
> >>You've lost every
> >>4th block of whatever size you striped on.  E.g. with a 64k stripe  
> >>size, you'll have lost
> >>from 128k-192k, 384k-448k, etc. - and there's almost definitely going  
> >>to be nothing
> >>salvagable from that.
> >>
> >>Graham
> >>
> >>_______________________________________________
> >>linux-lvm mailing list
> >>linux-lvm@redhat.com
> >>https://www.redhat.com/mailman/listinfo/linux-lvm
> >>read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
> >
> 
> 
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Heinz Mauelshagen                                 Red Hat GmbH
Consulting Development Engineer                   Am Sonnenhang 11
Storage Development                               56242 Marienrachdorf
                                                  Germany
Mauelshagen@RedHat.com                            PHONE +49  171 7803392
                                                  FAX   +49 2626 924446
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-