[linux-lvm] rescue data after hd crash
Graham Wood
gwood at dragonhold.org
Wed May 31 12:45:46 UTC 2006
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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