The vCenter Single Sign-On high availability mode can utilize a load balancer to increase the availability of the vCenter Single Sign-On service. You can use any SSL-enabled HTTP load balancer.

In high availability mode, two vCenter Single Sign-On nodes work with the same database, data, and user stores to ensure that vCenter Single Sign-On is not a single point of failure.

You can set up vCenter Single Sign-On in high availability mode with an Apache load balancing software. For more information see http://kb.vmware.com/kb/2076766.