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[Xen-users] very strange problem with reported uuid's of /dev/sdb and /dev/sdb1 combined with LVM

  • To: xen-users@xxxxxxxxxxxxxxxxxxx
  • From: Dolf Andringa <dolfandringa@xxxxxxxxx>
  • Date: Thu, 4 Jun 2009 00:07:09 +0200
  • Delivery-date: Wed, 03 Jun 2009 15:07:55 -0700
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  • List-id: Xen user discussion <xen-users.lists.xensource.com>

Hey Everyone,

I have a question which I think is related to Xen, so I hope you can help me.
I have Ubuntu Hardy server edition running in a Xen virtual machine
which I hire from a hosting provider.
The machine was running fine untill there was a power outage today.
Since the machine booted again, I have the following problem:

I have setup the primary image (/dev/sda1 and 2) using normal ext3. I
have a second disk image /dev/sdb in which I created one partition
which is used for LVM.
That one partition was the sole physical volume for a volume group.
Since the reboot, vgscan can't find that physical volume anymore and I
think that is due to a uuid problem.
When I run
vol_id -u /dev/sdb1 I get "Unknown volume type".
On the other hand
vol_id -u /dev/sdb returns "47caf26c-7491-4b24-a5cc-cd7825518ef3"
Wait a minute, dev/sdb returns a uuid? It shouldn't even be a partition right?

When I checked ls -l /dev/disk/by-uuid I got the following result:
lrwxrwxrwx 1 root root 10 2009-06-03 21:21
47caf26c-7491-4b24-a5cc-cd7825518ef3 -> ../../sdb1
lrwxrwxrwx 1 root root 10 2009-06-03 21:21
64db3117-17d9-463f-b560-7df7392a5816 -> ../../sda1
lrwxrwxrwx 1 root root 10 2009-06-03 21:21
c9e88347-58fd-4c8d-93d8-c0d8228d58eb -> ../../sda2

Hmm, even weirder. there is a uuid there for /dev/sdb1, and the uuid
is the value that vol_id returns for /dev/sdb. It really looks as
/dev/sdb and /dev/sdb1 got confused here or something.

To check I did fdisk -l (actually that was the first I did to be sure
the partition table was right) but that returns the correct partition
Disk /dev/sdb: 4294 MB, 4294967296 bytes
Disk identifier: 0x58a3ad78
  Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1         522     4192933+  8e  Linux LVM

My question is now if it would be possible that Xen or the Xen
administrator somehow mixed something up which caused the disk image
for /dev/sdb to be attached incorrectly to the virtual machine or
something, since it looks like /dev/sdb is the partition that should
actually be /dev/sdb1. I hope someone can help with this weird


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