You can configure vCenter Single Sign On for High Availability (HA) by installing two nodes in HA mode and putting them behind load balancing software. In HA mode, both the nodes work with the same database, use the same data, and have the same user stores.
1. SSO.PREETAM.COM act as a load balancer
2. SSO1.PREETAM.COM act as primary node
3. SSO3.PREETAM.COM act as Backup/Secondary node and is Joined to Primary node using High availability option shown below
4. SSODB.PREETAM.COM hosts the Database for SSO server.
For High Availability solution to work seamlessly, you must configured Load balancer
vCenter SSO installation Option
Below are the various options you see while installing vCenter SSO. In vSphere 5.1, vCenter Single Sign On (SSO) can be deployed in three modes: Basic, HA, or Multisite. HA mode can utilize a load balancer to increase the availability of the service
If you want to create to High availability or Multi-site vcenter SSO in future you must select Primary Node option as shown below & discussed above