Specifications

Administration Guide
26 VMware, Inc.
Figure 1-1. ESX Server core architecture
Virtualization
The!VMware!virtualization!layer!brings!hardware!virtualization!to!the!standard!Intel!
server!platform.!The!virtualization!layer!is!common!among!VMware!desktop!and!
server!products,!providing!a!consistent!platform!for!development,!testing,!delivery,!
and!support!of!application!workloads!from!the!developer!desktop!to!the!workgroup!to!
the!data!center.!
As!with!mainframe
!virtualization,!the!VMware!virtual!machine!offers!complete!
hardware!virtualization.!The!guest!operating!system!and!applications!(those!operating!
inside!a!virtual!machine)!can!never!directly!determine!which!specific!underlying!
physical!resources!they!are!accessing,!such!as!on!which!CPU!they!are!running!in!a!
multiprocessor!system!or!which!physical!memory!is!
mapped!to!their!pages.!The!
virtualization!of!the!CPU!incorporates!direct!execution:!non‐privileged!instructions!are!
executed!by!the!hardware!CPU!without!overheads!introduced!by!emulation.
The!virtualization!layer!provides!an!idealized!physical!machine!that!is!isolated!from!
other!virtual!machines!on!the!system.!It!provides!the!virtual!devices!that!map!
to!shares!
of!specific!physical!devices.!These!devices!include!virtualized!CPU,!memory,!I/O!buses,!
network!interfaces,!storage!adapters!and!devices,!human!interface!devices,!BIOS,!and!
others.
Each!virtual!machine!runs!its!own!operating!system!and!applications.!They!cannot!talk!
to!each!other!or!leak!data,!other!than!through!networking!mechanisms!similar!
to!those!
used!to!connect!separate!physical!machines.!This!isolation!leads!many!users!of!
VMware!software!to!build!internal!firewalls!or!other!network!isolation!environments,!
allowing!some!virtual!machines!to!connect!to!the!outside!while!others!are!connected!
only!through!virtual!networks!through!other!virtual!machines.