LVM problem

[Dan Coutu]

FYI, I do have Red Hat support on this case as well. I figured, and so 
far correctly, that I'd get faster answers here then there.
More below.

Ben Scott wrote:
> On Dec 14, 2007 12:23 PM, Dan Coutu <coutu at snowy-owl.com> wrote:
>   
>> Yes, I did them in that order. The reason that I did the mkfs ...
>>     
>
>   If you ran mkfs on a device that was a PV, after you ran "pvcreate",
> you've overwritten that PV's on-disk metadata, and basically wrecked
> that PV.
>
>   All the subsequent error messages about not finding the signature or
> UUID are likely because LVM has copies of the metadata in other
> locations.  So LVM knows there *should* be a PV there, but can't find
> it goes to look.  (I know LVM caches metadata under /etc/lvm/, and I
> think it also keeps copies of all the metadata for a VG in each member
> of the VG.)
>
>   
>> # vgextend VolGroup00 /dev/sdb
>>   /dev/cdrom: open failed: No medium found
>>   Volume group "VolGroup00" successfully extended
>>     
>
>   The /dev/cdrom part is likely a red herring.  Some LVM utilities
> scan all the possible devices in the system, looking for devices which
> might have PVs on them.  Since any IDE node (hda, hdb, hdc, etc.)
> might have a hard disk on it, it's going to probe all of those.  Once
> of those was likely your CD-ROM.
>
>   The second message, about the VG being successfully extended,
> indicates the PV was successfully added to the VG.  Then you blew it
> away with the mkfs.  ;-)
>   
Exactly. I had never seen any message like that when doing LVM things 
and it threw me off. I figured it was an error of some sort and that I 
had to take some other action. Feh.
>   
>> I've tried a new pvcreate but can't get rid of the uuid error message
>> and cannot do any vg* commands at all because of it.
>>     
>
>   You probably need to first do a vgreduce to remove the (wrecked) PV
> from the VG.  You may also need to do a pvremove to remove all traces
> of the wrecked PV; not sure on that.
>   
Yeah, the Red Hat support person suggested that. Only it doesn't work. 
The vgreduce that is. It gripes about
the unknown uuid. So the ball's back in his court. We shall see.

Dan