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Re: [linux-lvm] Corrupt PV (wrong size)



On Mar 5, 2012, at 4:31 PM, Stuart D. Gathman wrote:

> Long ago, Nostradamus foresaw that on Mar 5, Richard Petty would write:
> 
>> GOAL: Retrieve a KVM virtual machine from an inaccessible LVM volume.
>> 
>> DESCRIPTION: In November, I was working on a home server. The system
>> boots to software mirrored drives but I have a hardware-based RAID5
>> array on it and I decided to create a logical volume and mount it at
>> /var/lib/libvirt/images so that all my KVM virtual machine image
>> files would reside on the hardware RAID.
>> 
>> All that worked fine. Later, I decided to expand that
>> logical volume and that's when I made a mistake which wasn't
>> discovered until about six weeks later when I accidentally rebooted
>> the server. (Good problems usually require several mistakes.)
>> 
>> Somehow, I accidentally mis-specified the second LMV physical
>> volume that I added to the volume group. When trying to activate
>> the LV filesystem, the device mapper now complains:
>> 
>> LOG ENTRY
>> table: 253:3: sdc2 too small for target: start=2048, len=1048584192, dev_size=1048577586
>> 
>> As you can see, the length is greater than the device size.
> 
> I've run into something like this.  The issue was that the device was
> reporting the incorrect size.  It turned out to be buggy firmware in the SATA/USB adapter.  Using another adapter or connecting the drive directly
> to SATA made the problem go away.
> 
> You didn't mention the crucial details of which PV was on which kind of
> device.
> 
> You could try pvresize on sdc2, which could succeed if it won't invalidate
> any extents.  The size difference is small.
> 
> You might have changed the partition table on sdc, and the change would
> be written to disk (with a warning) but wouldn't be seen until you rebooted.
> 
> As long as the origin didn't change, pvresize will fix it, at most losing
> one extent at the end of sdc2.  (Size difference is 6606 sectors, ~3M.)

The system is a Dell PowerEdge 1900 and the PV is on a PERC 5 RAID controller. Other PVs on the same disk array appear to function fine.

Here I issued the pvresize command:

[root zeus] pvresize /dev/sdc2
  /dev/sdc2: cannot resize to 127999 extents as 128001 are allocated.
  0 physical volume(s) resized / 1 physical volume(s) not resized

No bueno.

--RP


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