[libvirt] Re: your mail

[Daniel P. Berrange]

On Thu, Oct 16, 2008 at 10:02:10AM +0200, Guido G?nther wrote:
> On Wed, Oct 15, 2008 at 09:59:12PM +0100, Daniel P. Berrange wrote:
> > When you get to that level of cleverness, it seems to me that it is verging 
> > on a complete re-implementation of DLM (distributed lock manager), which 
> > really, AFAIK, needs a proper cluster setup so it can safely fence 
> > mis-behaving nodes, and avoid quorum/split-brain problems.
> I've been toying with the idea of using DLM for libvirt earlier this
> year [1](but infered from other postings on the list that this would be out
> of scope for libvirt - probably should have asked). I looked at vm based
> locks then but having storage based locks is even better.
> 
> Currently you have to make sure "manually" that people using i.e.
> virt-manager[2] don't accidentally fire up VMs managed via e.g.
> rgmanager.
> 
> Having cluster wide storage based locks would be an awesome solution.

If libvirt is deployed in an environment where DLM is present & configured
I've no objection to libvirt making use of it. It should just be a soft
dependancy, where we also need to make a best effort for cases where DLM 
isn't around, even if that only works on a  single host, or with a subset
of storage backends. Give users the flexibility in terms of how they
deploy & integrate libvirt, without imposing too many constraints.

Daniel
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