Cisco Elastic Services Controller Active/Active HA Overview
ESC supports High Availability (HA) in the form of an Active/Active model. ESC Active/Active HA has three VMs as a cluster in one datacenter.. There are two datacenters. Between the two datacenters, one datacenter acts as active, another acts as standby. ESC Active/Active HA uses Openstack heat template to deploy the three VM cluster in a datacenter.
In a datacenter, ESC service runs on each VM; however, there is only one ESC on a datacenter that runs as cluster leader. DB service runs only on the leader. The ESC services on the other two ESC VMs run as cluster follower. The DB service is only active on ESC services leader VM.
DRBD synchronises the data among ESC VMs. The ESC service on the three ESC VMs connect to the active DB service. When a leader switchover happens, all the ESC service connects to the newly active DB service.