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Re: [Libvir] [RFC] Life-cycle Management of the domain



On Fri, Apr 20, 2007 at 11:35:00AM +0900, Saori Fukuta wrote:
> Hi, Daniel and Dan
> 
> Thank you for various comments.
> 
> Exactly. Libvirt is just a library and it is better to not keep states there. 
> The management states would be kept at end point server(eg. XenD, or QEMUD) or
> an application. So I would like to think again.
> 
> On Thu, 19 Apr 2007 16:18:28 +0100 "Daniel P. Berrange" wrote:
> > If we ignore case B, I think we still have lots of interesting
> > combos to think about:
> > 
> >   1. Static - change persistent config
> >   2. Dynamic - change live VM config
> >   3. Static and Dynamic - change persistent config, and live VM
> >   4. Static or Dynamic - if domain is inactive, change persistent
> >                          config, if it is active, change live VM
> > 
> > With the virDomainSetMem/MaxMem/VCPUs we in fact implement 3/4 depending
> > on the backend, because until we switch to XenAPI, that's basically the 
> > only option that is actually possible when talking to XenD.
> > 
> > So if you want to only change the persistent config, then you need to
> > redefine the entire domain XML file, using virDomainDefineXML() pasing
> > in the updated XML doc for the new inactive config. This lets you
> > indirectly do option 1.
> 
> Yes, that's a good idea. But I'm not sure how to change the presistent config
> without that libvirt maintain persiste state. Could you tell me your thinking ?
> Who has the XML file ?

This is already possible today actually. In Xen 3.0.4 or later there is the
lifecycle management APIs, so there is an API which lets you define a config
for a guest. So in this case we just convert from XML -> SEXPR, in the same
way that we do to boot a guest.  For older Xen, we simply write files straight
into /etc/xen.  The QEMUD daemon stores the XML files for QEMU/KVM in the
native libvirt format, so that's easy.

Regards,
Dan.
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