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----- Original Message -----
> 5. The act of applying affinity policies is now directly related to the
> act of launching instances, which is where it should be.

Well, that may be another discussion :). Something I have been pondering of late is the intersection of the server groups feature with the find host and evacuate instance proposal that allows evacuation without specifying a target host - instead re-scheduling the instance [1]. 

User expectations, I think, in this case would be that the group policies (however implemented) would stay with the VM throughout its lifecycle (or at least until the policy was explicitly removed/changed) and be taken into account when evacuating in this fashion. With the current model this expectation appears to be met for anti-affinity, but when it comes to affinity I would expect that the scheduler will place the evacuated instance right back where it came from as it doesn't have enough understanding to attempt to evacuate the entire group at once.

-Steve

[1] https://blueprints.launchpad.net/nova/+spec/find-host-and-evacuate-instance