[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
> 
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-- 

Regards,
Heinz    -- The LVM Guy --

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

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