find a bug:
at first there is only one zone.
create aggregate host1 in zone1
create aggregate host1 in zone1
then create boot a vm.
It will fail.
set default_availability_zone in cinder.conf
http://docs.openstack.org/draft/config-reference/content/section_volume-misc.html
set default_availability_zone in nova.conf
http://docs.openstack.org/draft/config-reference/content/list-of-compute-config-options.html
刘卫军：
OpenStack重要概念理解（Regions+Cells+Availability Zones+Host Aggregates等）
OpenStack Availability Zone和Aggregate Hosts理解
OpenStack Availability Zone和Aggregate Hosts理解
孔令贤：
【OpenStack】F版和G版中的Availability Zone
Openstack 中的zone ,aggregates和host及其应用
原文：http://www.cnblogs.com/shaohef/p/4857989.html