The document provides an overview of virtualization, including definitions, types of virtualization, and popular hypervisors. It discusses how virtualization addresses issues with underutilized servers in data centers by consolidating workloads. Full virtualization provides a complete hardware simulation but has challenges virtualizing certain architectures like x86. Paravirtualization modifies the guest OS, while hardware-assisted virtualization uses new CPU features to simplify virtualization. Memory, storage, network, and application virtualization are also summarized.

1. WELCOME

2. VIRTUALIZATION
Seminar Presented By:
Vishnu Ramakrishnan

3. The Modern Age of Computers

4. Problems in current Scenario
 The data-centres are:
 Full of under-utilized servers.
 Complicate in management.
 Power consumption
 Greater wattage per unit area than ever.
 Electricity overloaded.
 Cooling at capacity.
 Environmental problem

5. What is Virtualization
Virtualization -- the abstraction of computer resources.
Defenition : virtualization is a framework or methodology of dividing the resources
of a computer into multiple execution environments, by applying one or more
concepts or technologies such as hardware and software partitioning, time-
sharing, partial or complete machine simulation, emulation, and quality of service.
Virtualization hides the physical characteristics of computing resources from their
users, be they applications, or end users.
This includes making a single physical resource (such as a server, an operating
system, an application, or storage device) appear to function as multiple virtual
resources; it can also include making multiple physical resources (such as storage
devices or servers) appear as a single virtual resource.

6. Normal Computer System
Hardware
Operating
System
Applications

7. Virtualization - One Server for Multiple Applications/OS
Hardware
Operating
System
Applications
Hardware
Operating
System
Application
Hypervisor
Operating
System
Application
Operating
System
Application
Operating
System
Application
Operating
System
Applications
Hypervisor is a software program that manages multiple operating systems (or
multiple instances of the same operating system) on a single computer system.
The hypervisor manages the system's processor, memory, and other resources to
allocate what each operating system requires.
Hypervisors are designed for a particular processor architecture and may also
be called virtualization managers.

8. CPU Capacity Utilization

9. Why Virtualization
 Virtual machines can be used to consolidate the workloads of
several under-utilized servers to fewer machines, perhaps a single
machine. Related benefits are savings on hardware, environmental
costs, management, and administration of the server infrastructure.
 Virtual machines can be used to provide secure, isolated
sandboxes for running untrusted applications. Virtualization is an
important concept in building secure computing platforms.
 Virtual machines can provide the illusion of hardware, or hardware
configuration that you do not have (such as multiple processors).
Virtualization can also be used to simulate networks of independent
computers.
 Virtual machines can be used to run multiple operating systems
simultaneously: different versions, or even entirely different systems,
which can be on hot standby. Some such systems may be hard or
impossible to run on newer real hardware.

10. Why Virtualization
 Virtual machines allow for powerful debugging and performance monitoring.
You can put such tools in the virtual machine monitor, for example. Operating
systems can be debugged without losing productivity, or setting up more
complicated debugging scenarios.
 Virtual machines can isolate what they run, so they provide fault and error
containment. You can inject faults proactively into software to study its
subsequent behavior.
 Virtual machines are great tools for research and academic experiments. Since
they provide isolation, they are safer to work with. They encapsulate the entire
state of a running system: you can save the state, examine it, modify it, reload it,
and so on. The state also provides an abstraction of the workload being run.
 Virtualization can enable existing operating systems to run on shared memory
multiprocessors.
 Virtual machines can be used to create arbitrary test scenarios, and can lead to
effective quality assurance.
And plenty of other reasons……

11. Types of Virtualization
 Memory virtualization
 Desktop virtualization
 Platform virtualization (Close to Cloud Computing)
 Full virtualization
 Paravirtualization
 Hardware-assisted virtualization
 Partial virtualization
 OS-level virtualization
 Hosted environment (e.g. User-mode Linux)
 Storage virtualization
 Network virtualization
 Application virtualization
 Cross-platform virtualization
 Emulation or simulation
 Hosted Virtual Desktop

12. Full Virtualization
 Virtualization technique used to provide a complete simulation of
the underlying hardware, in the Virtual machine.
 One machine is accessed and manipulated by more than one users
or OS’s.
 All software (including all OS’s) capable of execution on the raw
hardware can be run in the virtual machine.
 Full virtualization has proven highly successful in cases when
 Sharing a computer system among multiple users,
 Isolating users from each other (and from the control program), and
 Emulating new hardware to achieve improved reliability, security and
productivity.

13. Full Virtualization
 example of full virtualization was that provided by the control
program of IBM's CP/CMS operating system. Each CP/CMS user was
provided a simulated, stand-alone computer.
Each such virtual machine had the complete capabilities of the
underlying machine, and (for its user) the virtual machine was
indistinguishable from a private system.

14. Full Virtualization - Requirements
 Equivalence: a program running under the VMM should exhibit a
behavior essentially identical to that demonstrated when running
on an equivalent machine directly.
 Resource control (safety): the VMM must be in complete control
of the virtualized resources.
 Efficiency: a majority of the machine instructions must be
executed without VMM intervention.

15. Full Virtualization - Challenges
 Interception and Simulation of privileged operations -- I/O
instructions
 The effects of every operation performed within a given virtual
machine must be kept within that virtual machine – virtual
operations cannot be allowed to alter the state of any other virtual
machine, the control program, or the hardware.
 Some machine instructions can be executed directly by the
hardware, E.g., memory locations and arithmetic registers.
 Other instructions that would "pierce the virtual machine" cannot be
allowed to execute directly; they must instead be trapped and
simulated. Such instructions either access or affect state information
that is outside the virtual machine.
 Some hardware is not easy to be used for full virtualization, e.g., x86

16. Challenges of x86 Hardware Virtualization
 The x86 architecture offers four levels of privilege
known as Ring 0, 1, 2 and 3 to operating systems
and applications to manage access to the
computer hardware.
 Virtualizing the x86 architecture requires placing a
virtualization layer under the OS (which expects to
be in the most privileged Ring 0) to create and
manage the virtual machines that deliver shared
resources.
 Solutions are :
> Binary translation (Eg: VMWare)
> OS assisted virtualization or paravirtualization.
> Hardware assisted virtualization

17.  Kernel code of non-virtualizable instructions are translated to replace
with new sequences of instructions that have the intended effect on the
virtual hardware.
 Each virtual machine monitor provides each Virtual Machine with all the
services of the physical system, including a virtual BIOS, virtual devices
and virtualized memory management.
 This combination of binary translation and direct execution provides Full
Virtualization as the guest OS is fully abstracted from the underlying
hardware by the virtualization layer.
 The guest OS is not aware it is being virtualized and requires no
modification.
 The hypervisor translates all operating system instructions on the fly and
caches the results for future use, while user level instructions run
unmodified at native speed.
 Examples
 VMware
 Microsoft Virtual Server
Binary Translation

18. Paravirtualization (OS Assisted)
 Paravirtualization – via a modified OS kernel as
guest OS
 Paravirtualization involves modifying the OS kernel to
replace non-virtualizable instructions with hypercalls that
communicate directly with the virtualization layer
hypervisor.
 The hypervisor also provides hypercall interfaces for other
critical kernel operations such as memory management,
interrupt handling and time keeping.
 Paravirtualization is different from full virtualization, where
the unmodified OS does not know it is virtualized and
sensitive OS calls are trapped using binary translation.
 It is very difficult to build the more sophisticated binary
translation support necessary for full virtualization,
modifying the guest OS to enable paravirtualization is
relatively easy.
 Paravirtualization cannot support unmodified OS
 Example:
 Xen -- modified Linux kernel and a version of Windows XP
Hardware
Paravirtualized
Guest OS
Application
Ring 2
Ring 1
Ring 0
Ring 3
Direct
Execution
of user and OS
Requests
Hypercalls to
the
Virtualization
Layer
replace
non-virtualiable
OS instructions
Virtualization layer

19.  Hardware vendors are rapidly embracing
virtualization and developing new features to
simplify virtualization techniques.
 First generation enhancements target
privileged instructions with a new CPU
execution mode feature that allows the VMM
to run in a new root mode below ring 0.
 Privileged and sensitive calls are set to
automatically trap to the hypervisor, removing
the need for either binary translation or
paravirtualization.
 Due to high hypervisor to guest transition
overhead and a rigid programming model,
binary translation approach currently
outperforms hardware assist implementations.
Hardware-Assisted Virtualization
Hardware
Guest OS
Application
Ring 2
Ring 1
Ring 0
Ring 3
Direct
Execution
of user and OS
Requests
OS requests traps
to VMM without
binary translation
or paravirtualization
VMM
Non-root
Mode
Privilege
Levels
Root Mode
Privilege
Levels

20. OS-level Virtualization
 OS-level virtualization – Server Virtualization method.
 kernel of an OS allows for multiple isolated user-
space instances, instead of just one.
 Each OS instance(or Container) looks and feels
like a real server to each user.
 This method virtualizes servers on the operating
system (kernel) layer. This creates isolated
containers on a single physical server and OS
instance to utilize hardware, software, data center
and management efforts with maximum efficiency.
 Virtual hosting environments commonly use
operating system–level virtualization, where it is
useful for securely allocating finite hardware
resources amongst a large number of mutually-
distrusting users.
Hardware
OS
Container 1
OS-Level Virtualization
Standard
Host OS
OS virtualization
layer
OS
Container 2
OS
Container 3

21. Application Virtualization
 Software technology that encapsulates application software from the underlying
operating system.
 A fully virtualized application is not actually installed in the traditional sense,
although it is still executed as if it is installed (runtime virtualization).
 Full application virtualization requires a virtualization layer. Application
virtualization layers replace part of the runtime environment normally provided
by the operating system. The layer intercepts all file and Registry operations of
virtualized applications and transparently redirects them to a virtualized location.
 Benefits :
 Allows applications to run in environments that do not suit the native
application (Eg: Wine).
 Uses fewer resources than a separate virtual machine.
 Improve portability, manageability and compatibility of applications.
 Improved security, by isolating applications from the operating system.
 Reduces system integration and administration costs in an Organization.

22. Memory Virtualization
 Memory virtualization decouples random access
memory (RAM) resources from individual systems in the
data center, and then aggregates those resources
into a virtualized memory pool available to any
computer in the cluster.
 The memory pool is accessed by the operating system
or applications running on top of the operating system.
 The distributed memory pool can then be utilized as a
high-speed cache, a messaging layer, or a large,
shared memory resource for a CPU or a GPU
application.
Machine memory
Physical memory
Virtual memory
Process 1 Process 2
VM1
Process 1 Process 2
VM2
Benefits :
• Improves memory utilization via
the sharing of scarce resources.
• Increases efficiency and
decreases run time for data
intensive and I/O bound
applications
• Allows applications on multiple
servers to share data without
replication, decreasing total
memory needs
• Lowers latency and provides
faster access than other
solutions.

23. Device and I/O Virtualization
 I/O virtualization environments are
created by abstracting the upper layer
protocols from the physical
connections.
 One physical adapter card appear as
multiple virtual network interface cards
(vNICs) and virtual host bus adapters.
 In the physical view, virtual I/O replaces
a server’s multiple I/O cables with a
single cable that provides a shared
transport for all network and storage
connections.
 Simplify management, lower costs and
improve performance of servers in
enterprise environments.
Benefits:
• Management agility: By abstracting upper layer
protocols from physical connections, I/O
virtualization provides greater flexibility, greater
utilization and faster provisioning when
compared to traditional architectures.
• Reduced cost: Virtual I/O lowers costs and
enables simplified server management by using
fewer cards, cables, and switch ports, while still
achieving full network I/O performance.
• Reduced cabling: In a virtualized I/O
environment, only one cable is needed to
connect servers to both storage and network
traffic. This can reduce data center cabling.
• Increased density: I/O virtualization increases the
practical density of I/O by allowing more
connections to exist within a given space.

24. Popular Hypervisors
 Xen
> Developed by Xen Project Team in 2003.
> Runs on Linux, BSD, Solaris.
 KVM
> Developed by OVA(Open Virtualization Alliance) and released in 2012.
> Supports many of Linux, BSD, Solaris, Windows, ReactOS, and AROS Research Operating
System.
 QEMU
> Open-Source, developed by QEMU Team.
> Runs on Linux, Windows, and some UNIX Platforms.
 VirtualBox
> Developed by Oracle Corporation in 2007.
> Runs on Linux, Mac OS X, Windows(from XP), Solaris, and OpenSolaris
 VMWare
> Developed by VMWare.inc in 1997
>Runs on Windows, Linux, Mac OS X

25. To Sum up…
 Virtualization provides the agility required to speed up IT operations,
and reduces cost by increasing infrastructure utilization.
 By minimizing user involvement, virtualization speeds up the process,
reduces labor costs and reduces the possibility of human errors.
 Binary translation is the most established technology for full
virtualization.
 Paravirtualization delivers performance benefits with maintenance
costs.
 Hardware assist is the future of virtualization, but it still has a long way
to go.

26. References
 VMWare ®
 IBM ®
 Microsoft®
 Intel ®
 AMD ®
 http://www.xen.org/
 http://en.wikipedia.org/
 http://www.parallels.com/
 http://www.webopedia.com/

27. Any Questions…..??

28. Thank You!