Re: [Xen-devel] [PATCH] xenctld - a control channel multiplexing daemon

[Daniel Stekloff <dsteklof@xxxxxxxxxx>]

On Friday 28 January 2005 01:17, Steven Hand wrote:
> > On Thu, 2005-01-27 at 08:19 -0600, Anthony Liguori wrote:
> > > Daniel Stekloff wrote:
> > > >Can't we add functionality in Xen to make domain id's unique? When
> > > >creating a new domain, the management tools can query the running (or
> > > >even suspended) domains and find a unique domain id to use. I think
> > > > you can tag a domains with their state.
> > >
> > > Yes, I think eventually domains have to have some sort of UUID.  I'm
> > > not convinced that those can't be mapped onto the current domain ids by
> > > configuration tools though.
> > >
> > > Here's a few scenarios to consider:
> > >
> > > 1) Someone suspends domain A to disk.  Domain A continues to run.
> > > Without stopping the original instance of Domain A, they start up the
> > > suspended image.
> >
> > At some point you need to make rules for operating, deciding based on
> > how you plan to use it what is the right way and the wrong way. A domain
> > needs to be unique. It can move through phases like being active or
> > being suspended. In the case you mention, I don't think Domain A can be
> > suspended and active at the same time. It's one or the other. If you
> > need to restart from a checkpoint, you clone the Domain A to Domain B.
> > We could think of it like process management.
>
> So it may be useful to revisit one of the original distinctions that
> we made, that between "domain" and "virtual machine":
>
>   - A domain is a Xen concept that has an associated domain struct,
>     allocation of physical memory, CPU time, event channels, etc. A
>     domain has an ID which is unique to all the domains currently
>     existing on a given physical machine. In general, think of "domain"
>     as the analog of "process".
>
>   - A virtual machine is the thing that inhabits a domain. It may
>     inhabit different domains (and hence have different domain IDs)
>     at various points in its life-cycle (e.g. due to suspend/resume,
>     live migration or even reboot).


Ok, I misunderstood. I thought you'd tie one to the other.

Is there a need for and how easy would it be to  reference a VM to domains 
over time or virtual resources to physical resources? What happens when an 
error occurs with a bit of hardware? Does Xen and Xen tools report it? What 
about the VM that's running on the system? What if a VM reports an error 
while running in one Domain and then the VM is moved to another Domain with 
different resources? Would we need to store history of VM to machine id and 
domain id? 

Or am I missing something?

Thanks,

Dan


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