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根据服务自身状况，HA 分为 Active/Active 和 Active/Passive 两种

• Active/Active: 适合于 stateless/stateful 服务，常用 Load Balancer + Keepalive(VIP) 配置 HA
• Active/Passive: 适用于 stateful 服务，常用 Load Balancer + Keepalive(VIP) + Pacemaker + Corosync 配置 HA

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OpenStack HA 实现

Database(Active/Active):

官方推荐：MySQL with Galera

AMQP(Active/Active):

官方推荐：RabbitMQ cluster

OpenStack API(Active/Active):

Keystone, Glance-api, Glance-registry, Neutron-server, Ceilometer-api, Dashboard 均为 stateless 服务，通过 Load Balancer + Keepalive 保证 HA，部署于 Apache server 可提高性能，Haproxy(1.5.0)支持 SSL。

• Loadbalance for OpenStack API
• Configuration SSL for haproxy
• Runs OpenStack API in apache

OpenStack scheduler(Active/Active):

Nova-scheduler, nova-conductor, nova-consoleauth, nova-novncproxy, ceilometer-collector, cinder-scheduler 等均为 stateless 服务，恰当的配置与 AMQP server 连接参数即可，具体详见社区文档

Memcached(Active/Active):

• 提高 Dashboard 的性能
• 解决 nova-consoleauth 单点问题

Network:

• neutron DHCP agent(Active/Passive)
• neutron L3 agent(Active/Passive)
• neutron metadata agent(Active/Passive)
• neutron DVR

以上三者均由 Pacemaker + Corosync 配置。

Storage:

Ceph 保证 Image storage, Volume storage, Nova backend 可靠性。