Virtual machines do not (and can not) directly connect to the fibre channel LUNs. Rather, the ESX server manages the storage pools to which it is attached. The ESX servers also manage load balancing. The ESX server needs to be zoned and connected to the storage LUNS like any other server, and the ESX server software determines which LUNs are viewed/accessible for certain VMs. This also hastens the ability to have other ESX servers view the LUNs for failover and HA configurations, since networked storage (via FC or iSCSI) is a requirement for disaster recovery. You can use raw LUNs for data drives—we have had a client configure ESX this way to facilitate array-based replication and recovery.
This was first published in May 2007