In a previous post, you learned how to segregate resources with , those methods allows the end user to specify where and on which types of resources their instances should be running.
At this post, you will learn how specify to nova where nova-scheduler should schedule your instances based on two policies. These policies define if instances should share the same hypervisor (affinity rule) or if not depending of user needs(anti-affinity rule).
First, you need to modify nova.conf and allow nova-scheduler to filter based on affinity rules. Add ServerGroupAntiAffinityFilter and ServerGroupAffinityFilter filters to scheduler default filter option.
# vi /etc/nova.conf
scheduler_default_filters=RetryFilter,AvailabilityZoneFilter,RamFilter,ComputeFilter,ComputeCapabilitiesFilter,ImagePropertiesFilter,CoreFilter,ServerGroupAntiAffinityFilter,ServerGroupAffinityFilter
Restart nova-scheduler to apply changes
systemctl restart openstack-nova-scheduler
Once nova-scheduler has been restarted, we can create a group of servers based on affinity policy (All instances at this group will be launched in the same hypervisor)
nova server-group-create instancestogethergroup affinity
+--------------------------------------+------------------------+---------------+---------+----------+
| Id | Name | Policies | Members | Metadata |
+--------------------------------------+------------------------+---------------+---------+----------+
| 27abe662-c37e-431c-9715-0d2137fc5519 | instancestogethergroup | [u'affinity'] | [] | {} |
+--------------------------------------+------------------------+---------------+---------+----------+
Now create two instances, add --hint group=GROUP-ID option to specify the group where instances will be members.
