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Don't think I'm much of an expert in this area, but I had a similar
issue that I worked through last week. I wasn't using mdadm, but I
don't really think this is a situation that is really relevant to
that.<br>
<br>
I posted the question on serverfault and got enough help to get me
through it. You can see it here:<br>
<a
href="http://serverfault.com/questions/275679/rescue-disk-is-unable-to-see-the-lvm-physical-volumes">http://serverfault.com/questions/275679/rescue-disk-is-unable-to-see-the-lvm-physical-volumes</a><br>
<br>
The suggestion that got me on the right track seems to be very
similar to your situation. How to recover your lvm configuration
with mdadm.<br>
<a
href="http://www.howtoforge.com/recover_data_from_raid_lvm_partitions">http://www.howtoforge.com/recover_data_from_raid_lvm_partitions</a><br>
<br>
The steps I went through were basically:<br>
* Recover config using dd per steps in that article<br>
* Recreate the physical volume using the same device<br>
* Do a pvcfgrestore on the recovered config from step 1<br>
<br>
That got me back up and running. I hope it helps.<br>
<pre class="moz-signature" cols="72">Anthony Nelson
Affinity Global Solutions
701.223.3565 Ext: 13
</pre>
<br>
On 6/5/2011 7:47 AM, Andreas Schild wrote:
<blockquote
cite="mid:BANLkTincWCwYQohG4D6uCU9JTZheV9w-wA@mail.gmail.com"
type="cite">Hi
<div>The first part might sound like I am in the wrong group, but
bear with me...</div>
<div>(I probably am, but I googled up and down RAID and LVM lists
and I am still stuck):</div>
<div>I have a software RAID 5 with 4 disks and LVM on top. I had
one volume group with two logical volumes (for root and data).</div>
<div>I wanted to upgrade capacity and started by failing a drive,
replacing it with a bigger one and let the RAID resync. Worked
fine for the first disk. The second disk apparently worked
(resynced, all looked good), but after a reboot the system hung.</div>
<div>After some back and forth with superblocks (on the devices,
never on the array) I was able to re-assemble the array clean.</div>
<div>The system still does not reboot though: "Volume group
"cmain" not found".</div>
<div><br>
</div>
<div>I booted a live cd, assembled the array and did a pvck on the
array (/dev/md0):</div>
<div>"Could not find LVM label on /dev/md0"</div>
<div>
<div>pvdisplay /dev/md0 results in:</div>
<div> No physical volume label read from /dev/md0</div>
<div> Failed to read physical volume "/dev/md0"</div>
</div>
<div><br>
</div>
<div>I do not have a backup of my /etc/ and therefore no details
regarding the configuration of the LVM setup (yes, I know...)</div>
<div>
All I have of the broken system is the /boot partition with its
content</div>
<div><br>
</div>
<div>Several questions arise:</div>
<div>- Is it possible to "reconstitute" the LVM with what I have?</div>
<div>- Is the RAID array really ok, or is it possibly corrupt to
begin with (and the reason no LVM labels are around)?</div>
<div>- Should I try to reconstruct with pvcreate/vgcreate? (I
shied away from any *create commands to not make things worse.)</div>
<div>- If all is lost, what did I do wrong and what would I need
to backup for a next time?</div>
<div><br>
</div>
<div>Any ideas on how I could get the data back would greatly be
appreciated. I am in way over my head, so if somebody
knowledgeable tells me: "you lost, move on" would be bad, but at
least would save me some time...</div>
<div><br>
</div>
<div>Thanks,</div>
<div>Andreas</div>
<div><br>
</div>
<pre wrap="">
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