[openstack-dev] [Scheduler] New scheduler feature - VM Ensembles

Gary Kotton gkotton at redhat.com
Wed Jan 9 09:43:47 UTC 2013

On 01/08/2013 09:00 PM, JC Martin wrote:
> Gary,
> This is a very interesting feature. I have a question on where the 
> definition of ensembles will reside. It seems from the linked document 
> that the definition of ensemble membership will only reside in Heat.

The idea is that the definition of the Ensemble will be maintained 
outside of Nova - for example by Heat or another tenant facing 
application. Only Ensembles that are currently active will be maintained 
in Nova. The interface can be expanded to enable suspending and 
rescheduling of the Ensembles.

> However, I would think that generic grouping capabilities in Nova 
> would be useful (e.g. to boot a group of VM). I can see that many of 
> such group operations might require the type of scheduling that is 
> available in Heat, but I would prefer that the basic notion of VM 
> group be implemented in Nova, with the right scheduling support, so 
> that it can be available without having Heat deployed and can also be 
> exposed in Horizon more easily.
> This could be implemented in a way similar to the host aggregates.

Storing and maintaining VM's that are not running is not in the scope of 
Nova and are better handled by applications like Heat.


> Thanks,
> JC
> From: Gary Kotton <gkotton at redhat.com <mailto:gkotton at redhat.com>>
> Organization: Red Hat
> Reply-To: <gkotton at redhat.com <mailto:gkotton at redhat.com>>, 
> "openstack-dev at lists.openstack.org 
> <mailto:openstack-dev at lists.openstack.org>" 
> <openstack-dev at lists.openstack.org 
> <mailto:openstack-dev at lists.openstack.org>>
> Date: Tue, 8 Jan 2013 15:27:20 +0200
> To: "openstack-dev at lists.openstack.org 
> <mailto:openstack-dev at lists.openstack.org>" 
> <openstack-dev at lists.openstack.org 
> <mailto:openstack-dev at lists.openstack.org>>
> Subject: [openstack-dev] [Scheduler] New scheduler feature - VM Ensembles
> Hi,
> The link 
> https://docs.google.com/document/d/1bAMtkaIFn4ZSMqqsXjs_riXofuRvApa--qo4UTwsmhw/edit 
> <https://docs.google.com/document/d/1bAMtkaIFn4ZSMqqsXjs_riXofuRvApa--qo4UTwsmhw/edit> 
> introduces the concept of a VM ensemble or VM group into Nova. An 
> ensemble will provide the tenant the ability to group together VMs 
> that provide a certain service or part of the same application. More 
> specifically it enables configuring scheduling policies per group. 
> This will in turn allow for a more robust and resilient service. 
> Specifically, it will allow a tenant to deploy a multi-VM application 
> that is designed for VM fault tolerance in a way that application 
> availability is actually resilient to physical host failure.
> Any inputs and comments will be greatly appreciated.
> Thanks
> Gary
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