libvirt users - Mar 2012 - Prevent starting a guest concurrently on multiple hosts when using shared storage

Hi list,

Scenario: Libvirt managing KVM-based guests on multiple physical
virtualisation hosts. These hosts are attached to some kind of shared
storage, be it NFS, GFS2 or whatever. Guest images live on the shared
storage so that VMs can be migrated (live or not) between the physical
hosts. Basically all Libvirt hosts have definitions of all guests.

How can I prevent the same guest from being started on different hosts
concurrently, either by accident or intentionally? As far as I can see
there is no locking or similar mechanism that would indicate to the
Libvirt daemon that a guest (and its VM image) is already running on/in
use by another host.

This might be a very basic question but I can't seem to find a
satisfying answer. Is it even possible? Or does using a shared storage
mean that one has to be really, really careful what to start, and where?
Is this even something for which Libvirt should be responsible?

Any insight is appreciated.

Thanks,

Andreas

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I've not done it myself, but see:

http://libvirt.org/locking.html

Dave

On Fri, Mar 16, 2012 at 02:28:01AM +0100, Andreas Ntaflos
wrote:
> Hi list,
> 
> Scenario: Libvirt managing KVM-based guests on multiple physical
> virtualisation hosts. These hosts are attached to some kind of shared
> storage, be it NFS, GFS2 or whatever. Guest images live on the shared
> storage so that VMs can be migrated (live or not) between the physical
> hosts. Basically all Libvirt hosts have definitions of all guests.
> 
> How can I prevent the same guest from being started on different hosts
> concurrently, either by accident or intentionally? As far as I can see
> there is no locking or similar mechanism that would indicate to the
> Libvirt daemon that a guest (and its VM image) is already running on/in
> use by another host.
> 
> This might be a very basic question but I can't seem to find a
> satisfying answer. Is it even possible? Or does using a shared storage
> mean that one has to be really, really careful what to start, and where?
> Is this even something for which Libvirt should be responsible?
> 
> Any insight is appreciated.
> 
> Thanks,
> 
> Andreas
> 

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