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[Sandy Walsh <sandy.walsh@xxxxxxxxxxxxx>]

Are you using Diablo or Trunk?

If you're using trunk the default scheduler is MultiScheduler, which uses Chance scheduler. I think Diablo uses Chance by default?

--scheduler_driver

Unless you've explicitly selected the LeastCostScheduler (which only exists in Diablo now) I wouldn't worry about those settings.

Did you explicitly define a scheduler to use?

________________________________
From: openstack-bounces+sandy.walsh=rackspace.com@xxxxxxxxxxxxxxxxxxx [openstack-bounces+sandy.walsh=rackspace.com@xxxxxxxxxxxxxxxxxxx] on behalf of Jorge Luiz Correa [correajl@xxxxxxxxx]
Sent: Thursday, November 10, 2011 6:27 AM
To: openstack@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Openstack] Four compute-node, everytime the 1st and 2nd are choosen

Is there a flag in nova.conf that permits we configure that? In documentation we can see that exists some algorithms used by scheduler. But, I don't know how to choose that one best fit our requirements.

Thanks!
:)

On Wed, Nov 9, 2011 at 1:36 PM, Ed Leafe <ed.leafe@xxxxxxxxxxxxx<mailto:ed.leafe@xxxxxxxxxxxxx>> wrote:
On Nov 9, 2011, at 7:51 AM, Razique Mahroua wrote:

> I use the default scheduler, in fact, I've never tunned it really.
> The hypervisors all run KVM

       This is where the flag is defined in nova.scheduler.least_cost.py<http://nova.scheduler.least_cost.py>:

 32 FLAGS = flags.FLAGS
 33 flags.DEFINE_list('least_cost_functions',
 34         ['nova.scheduler.least_cost.compute_fill_first_cost_fn'],
 35         'Which cost functions the LeastCostScheduler should use.')

       Since the default weighting function is 'compute_fill_first_cost_fn', which, as its name suggests, chooses hosts so as to fill up one host as much as possible before selecting another, the pattern you're seeing is expected. If you change that flag to 'nova.scheduler.noop_cost_fn', you should see the hosts selected randomly. The idea is that you can create your own weighting functions that will select potential hosts in a way that best fits your needs.


-- Ed Leafe


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- MSc. Correa, J.L.