Re: [Xen-devel] Re: [RFC] Switching store to use domain id's for keys

[Rusty Russell <rusty@xxxxxxxxxxxxxxx>]

On Mon, 2005-09-05 at 01:26 +0100, Steven Hand wrote:
> Rusty wrote:
> >As far as I can tell, UUIDs are a third identifier of domains, which buy
> >nothing over the existing two: names (cluster-wide unique, human
> >readable, slow), and domids (locally unique, fast).
> 
> Well one issue is that cluster-wide unique human readable names are 
> tricky to enforce.

A system with duplicate names is not really sane.  All user tools are
going to use names, so differentiation by uuids doesn't help.  Whether
name uniqueness is enforced or not I don't really mind: people are
creative, they can generate unique names all kinds off ways (even uuids
if that's what floats your boat).

> Right now what we need is something which refers
> to the same "virtual machine" regardless of which domain it currently
> inhabits. I.e. across save/restore, across migrate, etc. If this is 
> unique to a "virtual machine", then a 'fork' (when we get it) is going 
> to cause a new one of these to be created.

Sure, and the name fits these as well as UUID.  You cannot, in general,
meet your requirements, UUID or no, because you can fork and destroy the
original, etc.

> I guess we could try to use
> human readable stuff for this, but I think having the extra level of 
> indirection makes it easier. 

I disagree; more indirection, more concepts to master, more room for
confusion, more code, worse store layout, with no more features.

Seems all bad from where I'm sitting 8(
Rusty.
-- 
A bad analogy is like a leaky screwdriver -- Richard Braakman


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