Specifications

VMware, Inc. 27
Chapter 1 Introduction to VMware ESX Server
CPU Virtualization
Each!virtual!machine!appears!to!run!on!its!own!CPU,!or!set!of!CPUs,!fully!isolated!from!
other!virtual!machines,!with!its!own!registers,!translation!lookaside!buffer,!and!other!
control!structures.!Most!instructions!are!directly!executed!on!the!physical!CPU,!
allowing!compute‐intensive!workloads!to!run!at!near‐native!speed.!Privileged
!
instructions!are!performed!safely!by!the!patented!and!patent‐pending!technology!in!
the!virtualization!layer.
Memory Virtualization
While!a!contiguous!memory!space!is!visible!to!each!virtual!machine,!the!physical!
memory!allocated!may!not!be!contiguous.!Instead,!noncontiguous!physical!pages!are!
remapped!efficiently!and!presented!to!each!virtual!machine.!Some!of!the!physical!
memory!of!a!virtual!machine!might!be!mapped!to!shared!pages!or!to!pages!that
!are!
unmapped!or!swapped!out.!This!virtual!memory!management!is!performed!by!ESX!
Server!without!the!knowledge!of!the!guest!operating!system!and!without!interfering!
with!its!memory!management!subsystem.
Disk Virtualization
Support!of!disk!devices!in!ESX!Server!is!an!example!of!the!product’s!hardware!
independence.!Each!virtual!disk!is!presented!as!a!SCSI!drive!connected!to!a!SCSI!
adapter.!This!device!is!the!only!disk!storage!controller!used!by!the!guest!operating!
system,!despite!the!wide!variety!of!SCSI,!RAID,!and
!Fibre!Channel!adapters!that!might!
be!used!in!the!system.!
This!abstraction!makes!virtual!machines!more!robust!and!more!transportable.!You!do!
not!need!to!worry!about!the!potentially!destabilizing!drivers!that!you! might!have!to!
install!on!guest!operating!systems,!and!the!file!that!encapsulates!a!virtual!disk!is!
identical!no!matter!which!underlying!controller!or!disk!drive!is!used.
You!can!use!VMware!ESX!Server!effectively!with!storage!area!networks!(SANs).!ESX!
Server!supports!QLogic!and!Emulex!host!bus!adapters,!which!allow!an!ESX!Server!
computer!to!be!connected!to!a!SAN!and!to!see!the!disk!arrays!on!
the!SAN.
Network Virtualization
You!may!define!up!to!four!virtual!network!cards!within!each!virtual!machine.!Each!
virtual!network!card!has!its!own!MAC!address!and!may!have!its!own!IP!address!(or!
multiple!addresses),!as!well.!Virtual!network!interfaces!from!multiple!virtual!machines!
may!be!connected!to!a!virtual!switch.!Each!virtual!switch
!can!be!configured!as!a!purely!
virtual!network!with!no!connection!to!a!physical!LAN!or!can!be!bridged!to!a!physical!
LAN!by!one!or!more!of!the!physical!NICs!on!the!host!machine.!