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Thanks, guess this is entering the realm of scheduling & group scheduling and how "just the right" level of information is needed to do efficient group scheduling in nova/ironic vs the new/upcoming gantt service. 

To me splitting it into N single requests isn't group scheduling but is just more of a batch processor to make things more parallel. To me it seems like gantt (or heat) or something else should know enough about the topology to identify where to schedule a request (or a group request) and then gantt/heat should pass enough location information to nova or ironic to let it know what was selected. Then nova or ironic can go about the dirty work of ensuring the instances were created reliably.... Of course it gets complicated when multiple resources are involved; but nobody said it was going to be easy ;)

Sent from my really tiny device...

> On Jan 26, 2014, at 12:25 PM, "Robert Collins" <robertc at robertcollins.net> wrote:
> 
>> On 27 January 2014 08:04, Joshua Harlow <harlowja at yahoo-inc.com> wrote:
>> Doesn't nova already have logic for creating N virtual machines (similar to a group) in the same request? I thought it did (maybe it doesn't anymore in the v3 API), creating N bare metal machines seems like it would comply to that api?
> 
> It does, but it splits it into N concurrent single server requests so
> that they get spread out amongst different nova-compute processes -
> getting you parallelisation: and the code for single server requests
> is sufficiently complex that having a rarely used path that preserves
> the batch seems undesirable to me.
> 
> Besides which, as Ironic also dispatches work to many different
> backend workers, sending a batch to Ironic would just result in it
> having to split it out as well.
> 
> -Rob
> 
> -- 
> Robert Collins <rbtcollins at hp.com>
> Distinguished Technologist
> HP Converged Cloud
> 
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