[libvirt-users] Expanding an LVM Storage Pool

Osier Yang jyang at redhat.com
Tue Sep 24 06:45:05 UTC 2013


On 21/09/13 02:15, McEvoy, James wrote:
> I looked around but could not find any info on how to expand a libvirt managed LVM storage pool.  I do not see any virsh command to do it
> but I was successful using the vgexpand command to add some more storage once I destroyed the pools and then restarted it.
> I'd like to verify that this is the proper way to grow the storage in a libvirt LVM storage pool.

It's not the proper way in principle, but since libvirt doesn't support 
to extend
the volume groups for a logical pool yet, it's the only way now. One 
hint though,
you can try to refresh the pool by command "virsh pool-refresh" after 
the volume
group of the pool is extended. I.e, don't have to restart the pool.

>   And this brings up a second
> question, I did this without any VM running so I'd like to know what the impact of destroying a running pool is on running VMs.

If you have any VM which uses the pool's volume, it affects, especially 
if you
are using the volume with pool and volume name in domain config. e.g.

<source pool="$pool" volume="$volume"/>


>    
> Does taking the pool off-line cause any issues with running VMs or is the only affect that the pool is unavailable for management by libvirt?

Same as above. It's one of the thing in our TODO list : we probaly need 
to prevent
destroying the pool if any its volume is being used by any VM, 
especially if the volume
is used with pool and volume name in domain config.

>
> These are the commands that I ran to create my pool and expand it after a kickstart of the server:
>
> pvcreate -ff -y /dev/mapper/mpath?
> virsh pool-define-as --name  GuestVols --type logical --source-dev /dev/mapper/mpatha --target /dev/GuestVols
> virsh pool-build GuestVols
> virsh pool-start GuestVols
> virsh pool-autostart GuestVols
> virsh pool-destroy --pool GuestVols
> vgextend GuestVols /dev/mapper/mpath{b..d}
> vgdisplay GuestVols
> virsh pool-start --pool GuestVols
> virsh pool-info --pool GuestVols
>
> Is this the best way to create a managed pool across 4 LUNs? And to potentially expand the storage group in the future if more storage is needed?
>
>    --jim
>
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