Re: [Xen-users] Storage recovery question / recommendations

[Errol Neal <eneal@xxxxxxxxxxxxxxxxx>]

On Tue, 04/16/2013 12:46 AM, "mitch@xxxxxxxxxxxx" 
<mitch@xxxxxxxxxxxx> wrote:
> I did some reading - on vgcfgbackup / restore / display etc.
> 
> I think I'm still stuck - or I'm not getting it - how would the backup exist 
> - does xen / xcp automatically back up any existing LVM data on a new SR if 
> it sees one there first when it's mounting what it see's as a new drive? 
> Otherwise, the backups I have would only be for the newly re-initialized LVM 
> - meaning the data is still on the drive - or gone. Not in the backups - 
> right?

We aren't talking about backups of data. We are talking about metadata backups 
of the volume groups(s) themselves.They are created when you make changes to a 
VG like adding or removing an LV..  So long as actually haven't written any 
data to the new volume group, then it should be possible to restore the 
previous layout and logical volumes. You should review each of the files and 
see which one matches the characteristics of the VG that you are trying to 
recover.

> Maybe I should restate what happened in case I was unclear... I think I might 
> have been - sorry about that - in trying to be concise I might have 
> oversimplified.
> 
> I installed 1.6 on a machine that had 1.1 - it wasn't an upgrade in the 
> proper sense - it didn't detect the drives in the same order. So I 
> reinstalled. Plus I wanted to break up a different SR (which was one LVM 
> spanning a couple disks into separate SR's).

Well if you didn't upgrade and just reinstalled, also reformatting the root 
partition, then your are right, you don't have any backups. 

> Is there a tool that can extract the details I need from the drive itself? 
> Like a backup of a partition table or "superblock" etc.?
> 

You can try testdisk. I've never used it for lvm recovery, but it's saved my 
ass for other stuff. Here is an example of someone using it for LVM recovery:

http://itknowledgeexchange.techtarget.com/linux-lotus-domino/recovering-files-from-an-lvm-or-ext3-partition-with-testdisk/


Let me know how it works out.. 

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