[ClusterLabs] convert already clustered LVM to cLVM

[Eric Ren]

Hi Cristiano,

On Wed, Jun 28, 2017 at 08:46:55AM +0000, Cristiano Coltro wrote: 
> Hi all,
> 
> A brief History
> 
> Customer of mine has setted up a SLES 11 sp3 and SLES11sp4 HA environment and he has some LVM as resources.
> 
> When he tries to expand LVM for a "need of space" reason he wasn't able to extend cause a corruption of metadata that even if recovered with vgcfgrestore doesn't heal.
> 

It's dangerous to have a non-clustered VG for shared disks. The
corruption will _not_ surprise me if the VG is on shared disks
which means that the disks have possibility to be attached to more than
one node in the cluster.

> The customer has not configured LVM with the "c"( clustered ) attribute
> 
>    95   VG        #PV #LV #SN Attr   VSize   VFree
>    96   vg00        1   3   0 wz--n- 279.22g  88.22g
>    97   vgWP4       2  10   0 wz--n-  49.97g   5.97g
> 
> that prevents to extend the LVM and gets
> 
> 83664       Setting global/locking_type to 3
> 83665       global/wait_for_locks not found in config: defaulting to 1
> 83666       Cluster locking selected.
> 83667     connect() failed on local socket: No such file or directory
> 83668     Internal cluster locking initialisation failed.

Please check if the clvmd daemon is running well, which is a must when
locking_type is 3.

> 83669       Setting global/fallback_to_local_locking to 1
> 83670       locking/fallback_to_local_locking not found in config: defaulting to 1
> 83671     WARNING: Falling back to local file-based locking
> 
> 
> Cause he has the file locking set to 3 ( correctly ) but he must have the "c" attribute to work properly.
> 
> Coming to my question:
> 
> 
>   *   Is there a way to convert the LVMs without pain to cLVMs?  I know that technically a vgchange -cy do the trick but I'm not sure which impacts it can have.

No, if a clustered VG is what you need. "vgchange -cy" will give the VG
cluster-wide protection, which is needed if the VG is shared among
nodes. It won't
break anything, but otherwise making a non-clustered VG on shared disks
is dangerous, because the metadata on the shared disk may be corrupted
unexpectedly from more than one nodes.

Thanks,
Eric

> 
> Thanks in advance
> Cristiano
> 
> Cristiano Coltro
> Premium Support Engineer
> 
> mail: cristiano.coltro at microfocus.com<mailto:cristiano.coltro at microfocus.com>
> mobile: +39 335 1435589
> phone +39 02 36634936
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