openstack team mailing list archive

[Ed Leafe <ed.leafe@xxxxxxxxxxxxx>]

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:

 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