Transcript Presentation

Ashtyn Hemendinger
Natalie Mark
Hong Ding
Joseph
Minjae Lee
 Platform Virtualization: technique
used to
implement a certain kind of virtual
machine environment: one that provides
a complete simulation of the underlying
hardware.
 In full virtualization, the virtual machine
simulates enough hardware to allow an
unmodified "guest" OS (one designed for
the same instruction set) to be run in
isolation.
 Hardware-assisted
virtualization was first
introduced on the IBM System/370 in
1972, for use with VM/370, the first virtual
machine operating system. Virtualization
was eclipsed in the late 1970s, with the
advent of minicomputers that allowed for
efficient timesharing, and later with the
commoditization of microcomputers.
To compensate for these architectural limitations,
virtualization of the x86 architecture has been
accomplished through two methods: full
virtualization or paravirtualization. Both create
the illusion of physical hardware to achieve the
goal of operating system independence from the
hardware but present some trade-offs in
performance and complexity.
 Well-known implementations of hardwareassisted x86 virtualization include VMware
Workstation (for 64-bit guests only), Xen 3.x
(including derivatives like Virtual Iron), Linux
KVM and Microsoft Hyper-V.

 Hardware-assisted
virtualization reduces
the maintenance overhead of
paravirtualization as it restricts (ideally,
eliminates) the amount of changes
needed in the guest operating system. It
is also considerably easier to obtain
better performance. A practical benefit
of hardware-assisted virtualization that
has been cited by VMware engineers and
Virtual Iron.
 Hardware-assisted
virtualization requires
hardware support, which has only
recently (2007) become available on x86
processors.
 A “pure” hardware-assisted virtualization
approach, using entirely unmodified
guest operating systems, involves many
VM traps, and thus high CPU overheads;
this limits scalability and the efficiency of
server consolidation.
 High
CPU overheads can be mitigated by
the use of paravirtualized drivers; the
combination has been called “hybrid
virtualization”.
 Though there are lots of setbacks and
defects, virtualization has potential to be
very useful in the future when the
technology becomes established.