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On Tue, 2014-12-30 at 14:52 +0800, Lingxian Kong wrote:
> Just as what Jay Lau said, 'nova hypervisor-show <hypervisor_id>'
> indeed returns host ip address, and there are more other information
> included than 'nova host-describe <hostname>'. I feel a little
> confused about the 'host' and 'hypervisor', what's the difference
> between them? For cloud operator, maybe 'host' is more usefull and
> intuitive for management than 'hypervisor'. From the implementation
> perspective, both 'compute_nodes' and 'services' database tables are
> used for them. Should them be combined for more common use cases?

Well, the host and the hypervisor are conceptually distinct objects.
The hypervisor is, obviously, the thing on which all the VMs run.  The
host, though, is the node running the corresponding nova-compute
service, which may be separate from the hypervisor.  For instance, on
Xen-based setups, the host runs in a VM on the hypervisor.  There has
also been discussion of allowing one host to be responsible for multiple
hypervisors, which would be useful for providers with large numbers of
hypervisors.
-- 
Kevin L. Mitchell <kevin.mitchell at rackspace.com>
Rackspace