[openstack-dev] [nova] Proposal: Move CPU and memory allocation ratio out of scheduler

Day, Phil philip.day at hp.com
Thu Jun 12 15:37:09 UTC 2014

> -----Original Message-----
> From: Jay Pipes [mailto:jaypipes at gmail.com]
> Sent: 09 June 2014 19:03
> To: openstack-dev at lists.openstack.org
> Subject: Re: [openstack-dev] [nova] Proposal: Move CPU and memory
> allocation ratio out of scheduler
> On 06/09/2014 12:32 PM, Chris Friesen wrote:
> > On 06/09/2014 07:59 AM, Jay Pipes wrote:
> >> On 06/06/2014 08:07 AM, Murray, Paul (HP Cloud) wrote:
> >>> Forcing an instance to a specific host is very useful for the
> >>> operator - it fulfills a valid use case for monitoring and testing
> >>> purposes.
> >>
> >> Pray tell, what is that valid use case?
> >
> > I find it useful for setting up specific testcases when trying to
> > validate things....put *this* instance on *this* host, put *those*
> > instances on *those* hosts, now pull the power plug on *this* host...etc.
> So, violating the main design tenet of cloud computing: though shalt not care
> what physical machine your virtual machine lives on. :)
> > I wouldn't expect the typical openstack end-user to need it though.
> Me either :)

But the full set of system capabilities isn't only about things that an end-user needs - there are also admin features we need to include.

Another use case for this is to place a "probe" instance on specific hosts to help monitor specific aspects of the system performance from a VM perspective.

> I will point out, though, that it is indeed possible to achieve the same use
> case using host aggregates that would not break the main design tenet of
> cloud computing... just make two host aggregates, one for each compute
> node involved in your testing, and then simply supply scheduler hints that
> would only match one aggregate or the other.

Even I wouldn't argue that aggregates are a great solution here ;-)   Not only does having single node aggregates for every host you want to force to seem a tad overkill, the logic for this "admin" feature includes by-passing the normal scheduler filters, 

> Best,
> -jay
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