And despite all the different names that VMware has come up with for the vSphere package - vCompute, vNetwork, and vStorage, all part of what VMware chief executive officer Paul Maritz called the "21st century software mainframe" at EMC's analyst conference in early March - most of the features in vSphere are, according to Balkansky, in the hypervisor. That's ESX Server 4.0 for servers and ESXi 4.0 for the embedded version that ships on flash drives inside servers. But you won't see VMware saying ESX Server much in the announcement today or in its marketing materials.