[mythtv-users] LVM Problem -- Please Help

Tom+Dale tdmyth at yahoo.com
Tue Aug 15 13:01:08 UTC 2006

chris at cpr.homelinux.net wrote: On Mon, Aug 14, 2006 at 03:52:19PM -0700, Tom+Dale wrote:
> >> I was suspicious about the new drive because it was clicking loudly, so I
> >> shut down cleanly and disconnected it.

This can be caused by a lot of problems, not all of which are 
fatal.  Since it's a new drive you just added to your machine, the 
power supply has to be at least considered.  If the clicking sound 
is only once every 1 or 2 seconds then it could be caused by the 
drive power-cycling.  Try unplugging *all* of your other hard 
drives (so the machine won't try to boot) and see if the clicking 
goes away.  If so then you need to buy a bigger power supply.  
Another cause of clicking is a failure of the drive's controller 
card.  On my old Western Digital drives that usually resulted in a 
click rate of around 4Hz.  If the clicking is very spread out or 
doesn't start right away when the power is turned on then it could 
be a thermal issue.

> >> The system reports a missing physical volume of UUID ### and then reports
> >> an unknown physical volume with the same UUID.

I use mdadm instead of lvm, but the rules are probably similar: if 
you specify an actual device name for an array component then the 
array will not recognize that component if the device name is 
changed.  The trivial work-around in mdadm is to change the config 
file so that it searches for components using only the uuid.

> 1) Is the error about not finding /dev/sda a definitive reason as to why the
> other commands failed (pvcreate -u...  & vgcfgrestore -tn ...)?  It seems to me
> that the drive needed a successful pvcreate in order to be added to the volume
> group, but I confess that I don't remember precisely how things transpired.  So
> if linux doesn't see it right away, does that mean it's dead?

To answer the first part of that question: yes.  If Linux did not 
find a device at /dev/sda then almost any command that refers to 
/dev/hda will fail.  As for the last part: no.  Just because Linux 
didn't see the drive doesn't mean it's dead.  There are lots of 
reasons why Linux might not see a drive, ranging from BIOS settings 
to missing kernel modules.

> 2) If the drive was not dead, should linux have picked up the /dev/sda on boot
> once it was re-connected, despite my earlier mistake of booting once without it
> connected?

Yes.  Assuming the drive is in fact not dead and that you're still 
running the same kernel (with SATA support loaded) and the cables 
are all correct, then you should be able to see it mentioned in 
/var/log/messages as part of the boot messages.

Thanks for the help, Chris.  I had not mentioned earlier that this is a new motherboard and power supply, too.  I have checked the BIOS at boot, and learned that the SATA drive does not show up unless I probe for it.  I know that is different than when it was installed the very first time.  Also, the probe returns what must be a guess, because it is incorrectly identifying the drive.  When it was installed on Friday, the system recognized it correctly with the drive model number and size whereas now it comes up with something else entirely.  Looking at the boot messages, I see that the _volume_ reports a failure to mount, but I don't see the drive mentioned.
>> 3) If the drive is okay, and /dev/sda were being recognized, how would I go
>> about re-linking the UUID to the physical volume?
>> 4) Can an identical replacement drive be put in and given the UUID in order
>> to recover data from the rest of the logical volume?
I have made arrangements to RMA this drive (NewEgg really has excellent customer service).  So my other questions weigh heavily on my mind (i.e., will I lose ~200GB of data from the still functioning drives that were part of this LVM? Or will I be able to put in an identical, functioning replacement and give it a UUID that the LVM likes in order to access my original drives?

Thanks again

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