Open Stack

The flag (of type list) you can use is "--least_cost_functions"
Multiple algorithms can be specified, the default one is "compute_fill_first_cost_fn" which gives priority to the compute host (XenServer/ESX etc.) with more free RAM.

Regards,
Sateesh

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From: openstack-bounces+sateesh.chodapuneedi=citrix.com at lists.launchpad.net [mailto:openstack-bounces+sateesh.chodapuneedi=citrix.com at lists.launchpad.net] On Behalf Of Razique Mahroua
Sent: Thursday, November 10, 2011 4:12 PM
To: Jorge Luiz Correa
Cc: openstack at lists.launchpad.net
Subject: Re: [Openstack] Four compute-node, everytime the 1st and 2nd are choosen

+1 :)

Razique Mahroua
razique.mahroua at gmail.com<mailto:razique.mahroua at gmail.com>

[cid:image002.jpg at 01CC9FD5.EC50CAF0]

Le 10 nov. 2011 à 11:27, Jorge Luiz Correa a écrit :


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 at rackspace.com<mailto:ed.leafe at rackspace.com>> 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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