When Cloud Foundation is deployed in a multi-rack environment, bare-metal provisioning and subsequent installation and configuration of software components (e.g., vCenter, NSX, SDDC Manager on host 0) is executed on each rack sequentially. Though there is an instance of SDDC Manager on each physical rack, you can control and manage your Cloud Foundation system through a single interface.
SDDC Manager is highly available. The SDDC Manager instance in the management cluster of the first physical rack is the leader, while the SDDC Manager on each additional physical rack is a secondary instance. To manage this cluster of SDDC Manager services, Cloud Foundation uses Zookeeper and Cassandra as a distributed cluster management service and as shared distributed datastore.
Zookeeper runs as a ZK server process instance within the SDDC Manager VM. The SDDC Manager process communicates with Zookeeper servers using a Zookeeper client handle.