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

From: chris <cspot@gmx.at>
To: mauelshagen@redhat.com,
	LVM general discussion and development <linux-lvm@redhat.com>
Subject: Re: [linux-lvm] rescue data after hd crash
Date: Thu, 01 Jun 2006 00:39:39 +0200	[thread overview]
Message-ID: <optafs8dpg51dxvh@notebook_chl.intern> (raw)
In-Reply-To: <20060531213154.GA2236@redhat.com>

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 ungï¿½ltig"
  (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
>>
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>