When determining the license entitlement required you must account for all the available cpu's that a given host has access to. If the physical host in question supports Virtualization that will restrict the the cpu's assigned to the guest os and is supported as a platform for installing Storage Foundation (Solaris Zones for example would not be a virtual platform that would satisfy this) then you can license a subset of the machine for use with Storage Foundation. Otherwise, you will have to license the entire system.
Given that the platform is Red Hat, please take a look at the following white paper for a more detailed explanation on how Storage Foundation works in a Linux VM environemnt:
https://www-secure.symantec.com/connect/articles/veritas-cluster-server-application-note-support-ker...
You may want to consider upgrading to 5.1 SP1 to enable this feature. Additionally, support for 4.x is coming to an end fairly soon for most platforms.
Hope this helps.
Joe D
