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" <robe...@robertcollins.net> 
> wrote:
> 
>> On 27 January 2014 08:04, Joshua Harlow <harlo...@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 <rbtcoll...@hp.com>
> Distinguished Technologist
> HP Converged Cloud
> 
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