On Sat, Oct 15, 2011 at 10:34:55PM +0200, Yaniv Kaul wrote:
> On 10/15/2011 10:19 PM, Dan Kenigsberg wrote:
> <SNIP>
> >I find it quite awkward for ovirt-engine to send code to MOM. It is not like 
> >the
> >programmers of ovirt-engine are smarter than you and could devise a better
> >policy. It *is* important to have "ballooning profiles" attached to guests 
> >(e.g.
> >"this VM is holy, do not balloon unless host is in deep manure") or hosts 
> >("keep
> >100Mb free at all costs"). I think that defining the available profiles is 
> >the
> >business of MOM - no one can do it better.
> >
> >Dan.
> I disagree, for one reason - the engine has an overall view of the
> system, not just of a single node.
> However, I haven't found yet where it can be advantage. I'm sure
> there are such cases, though.
> The knowledge of an operating system, its properties (to which user
> it belongs, its priority, is it related to another VM, ...) probably
> has some value.

Sure, but these should be a finite set policies and their parameters. Management
layer should be provided with useful knobs and handles, not the ability to push
generic code.

Can you ever envisage ovirt-engine compiling a completely new policy on its own
volition? This would require AI capabilities out of its current scope. The
Engine may have several policies dumped in its database, and it would have to
apply one of them to a host every time it changes to Up. The only advantage I
see in this is that introducing a new policy in a new Engine version is simpler,
and does not require updating all of its nodes.

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