What are the two requirements for HA to work?

A.
Hosts need to have compatible CPU.

B.
Hosts need to have shared storage.

C.
Hosts should have a static IP address.

D.
You need 2 VMkernel Ports

Explanation:
http://pubs.vmware.com/vsphere-50/topic/com.vmware.ICbase/PDF/vsphere-esxi- vcenter-server-50-availability-guide.pdf