The filter scheduler uses the
scheduler_weight_classes
configuration parameter to calculate the weights of hosts.
The value of this parameter defaults to
nova.scheduler.weights.all_weighers,
which selects the only weigher available -- the
RamWeigher. Hosts are then weighed and sorted with the
largest weight winning.
scheduler_weight_classes=nova.scheduler.weights.all_weighers ram_weight_multiplier=1.0
The default behavior is to spread instances across all
hosts evenly. Set the
ram_weight_multiplier configuration
parameter to a negative number if you prefer stacking
instead of spreading.
