Compute uses the nova-scheduler service to
determine how to dispatch compute and volume requests. For example, the nova-scheduler service determines which host a VM should
launch on. The term host in the context of filters means a physical node that has a
nova-compute service running on it.
You can configure the scheduler through a variety of options.
Compute is configured with the following default scheduler options:
scheduler_driver=nova.scheduler.multi.MultiScheduler compute_scheduler_driver=nova.scheduler.filter_scheduler.FilterScheduler scheduler_available_filters=nova.scheduler.filters.all_filters scheduler_default_filters=AvailabilityZoneFilter,RamFilter,ComputeFilter least_cost_functions=nova.scheduler.least_cost.compute_fill_first_cost_fn compute_fill_first_cost_fn_weight=-1.0
By default, the compute scheduler is configured as a filter scheduler, as described in the next section. In the default configuration, this scheduler considers hosts that meet all the following criteria:
Are in the requested availability zone (
AvailabilityZoneFilter).Have sufficient RAM available (
RamFilter).Are capable of servicing the request (
ComputeFilter).
For information on the volume scheduler, refer the Block Storage section of OpenStack Cloud Administrator Guide for information.
