在Openstack 实际的应用中，经常会被客户或者Boss问到，我创建的虚拟机在后端众多物理机上是怎么分配的。
这时你最好不要答“你不用考虑后面分配的细节，我们的云会自动处理”。
或者这样的：我后端的计算节点，有一批机器是新机器，特别好，一些是旧机器，性能不好，我想把关键应用放到新机器上，普通应用到放到旧机器上。
上面的场景通过Openstack的aggregate即可以解决.
在未应用aggregate之间，我们用nova-manage service list 来查看平台服务:
root@AuthServer:~# nova-manage service list Binary Host Zone Status State Updated_At nova-consoleauth AuthServer internal enabled :-) 2013-04-24 02:35:39 nova-cert AuthServer internal enabled :-) 2013-04-24 02:35:38 nova-conductor AuthServer internal enabled :-) 2013-04-24 02:35:38 nova-scheduler AuthServer internal enabled :-) 2013-04-24 02:35:39 nova-compute AuthServer nova enabled :-) 2013-04-24 02:35:35 nova-compute KVMCompute nova enabled :-) 2013-04-24 02:35:30 nova-compute VmWareCompute nova enabled :-) 2013-04-24 02:35:34 nova-scheduler VmWareCompute internal enabled :-) 2013-04-24 02:35:26 nova-scheduler KVMCompute internal enabled :-) 2013-04-24 02:35:27
他们全部默认在nova Zone中（如果你没有配置node_avalibility_zone的话）,
在通过aggregate 配置好主机集合后，service list变成了.
root@AuthServer:~# nova-manage service list Binary Host Zone Status State Updated_At nova-consoleauth AuthServer internal enabled :-) 2013-04-24 02:35:39 nova-cert AuthServer internal enabled :-) 2013-04-24 02:35:38 nova-conductor AuthServer internal enabled :-) 2013-04-24 02:35:38 nova-scheduler AuthServer internal enabled :-) 2013-04-24 02:35:39 nova-compute AuthServer zone52 enabled :-) 2013-04-24 02:35:35 nova-compute KVMCompute zone51 enabled :-) 2013-04-24 02:35:30 nova-compute VmWareCompute zone53 enabled :-) 2013-04-24 02:35:34 nova-scheduler VmWareCompute internal enabled :-) 2013-04-24 02:35:26 nova-scheduler KVMCompute internal enabled :-) 2013-04-24 02:35:27
这样，我们可以用过Openstack的api ，创建虚拟机，直接指定avalibility_zone，让虚拟机指定创建到某个主机组中。
{ "server":{ "name":"server-1", "availability_zone":"zone52", "imageRef":"87589e22-fc26-4ab0-8b15-948823b00a5e", "flavorRef":"1" } }
主机组支持一对多，可以灵活配置，具体配置可参考nova -help内容.
还可以，直接指定到某个zone中的某台主机：
{ "server":{ "name":"server-1", "imageRef":"87589e22-fc26-4ab0-8b15-948823b00a5e", "availability_zone" : "zone5153:VmWareCompute", "flavorRef":"1" } }
下面是我的配置:
共创建了三个主机组，每个一台机器方便测试:
root@AuthServer:~# nova aggregate-list +----+------+-------------------+ | Id | Name | Availability Zone | +----+------+-------------------+ | 4 | agg1 | zone51 | | 5 | agg2 | zone52 | | 6 | agg3 | zone53 | +----+------+-------------------+ root@AuthServer:~# nova aggregate-details 4 +----+------+-------------------+-----------------+-----------------------------------+ | Id | Name | Availability Zone | Hosts | Metadata | +----+------+-------------------+-----------------+-----------------------------------+ | 4 | agg1 | zone51 | [u'KVMCompute'] | {u'availability_zone': u'zone51'} | +----+------+-------------------+-----------------+-----------------------------------+ root@AuthServer:~# nova aggregate-details 5 +----+------+-------------------+-----------------+-----------------------------------+ | Id | Name | Availability Zone | Hosts | Metadata | +----+------+-------------------+-----------------+-----------------------------------+ | 5 | agg2 | zone52 | [u'AuthServer'] | {u'availability_zone': u'zone52'} | +----+------+-------------------+-----------------+-----------------------------------+ root@AuthServer:~# nova aggregate-details 6 +----+------+-------------------+--------------------+-----------------------------------+ | Id | Name | Availability Zone | Hosts | Metadata | +----+------+-------------------+--------------------+-----------------------------------+ | 6 | agg3 | zone53 | [u'VmWareCompute'] | {u'availability_zone': u'zone53'} | +----+------+-------------------+--------------------+-----------------------------------+
最后提一下，如果主机数量比较少，不需要使用aggregate,直接使用默认的zone nova即可：
--availability-zone <availibility-zone>:<compute-host>
#nova boot --image aee1d242-730f-431f-88c1-87630c0f07ba --flavor 1 --availability-zone nova:nova-1 testhost