Unit II
• Introduction to virtualization, Different approaches to
virtualization, Hypervisors, Machine Image, Virtual
Machine (VM), Compute options in the cloud, Exploring
IaaS with Compute Engine, Configuring elastic apps with
auto scaling, Basics of virtualization and implementation
challenges. System virtualization
technologies-architectures and internals. KVM, Xen,
VMware.
• Memory virtualization-virtualization techniques,
ballooning, deduplication and sharing. Network and
storage virtualization, Virtual machine migration and
replication techniques pre-copy and post- copy techniques,
applicability to system availability
Virtualization
• One of the main cost effective, hardware reducing, and
energy saving techniques used by cloud providers is
virtualization.
• Virtualization allows to share a single physical instance
of a resource or an application among multiple customers
and organizations at one time.
• It does this by assigning a logical name to a physical
storage and providing a pointer to that physical resource
on demand.
• It provide a virtual environment for not only executing
applications but also for storage, memory, and
networking.
BENEFITS OF VIRTUALIZATION
1. More flexible and efficient allocation of resources.
2. It lowers the cost of IT infrastructure.
3. Remote access and rapid scalability.
5. High availability
4. disaster recovery.
6. IT infrastructure on demand.
7. Enables running multiple operating systems.
Types of Virtualization
1.Application Virtualization.
2.Network Virtualization.
3.Desktop Virtualization.
4.Storage Virtualization.
5.Server Virtualization.
6.Data virtualization.
Virtual Machines
• A machine with virtualization software can host numerous
applications, including those that run on different
operating systems, on a single platform.
• Virtualization is a technique, which allows to share single
physical instance of an application or resource among
multiple organizations or tenants (customers).
• It does so by assigning a logical name to a physical
resource and providing a pointer to that physical
resource on demand
Host machine, Guest machine
• The machine on which the virtual machine is created is
known as host machine
• Virtual machine is referred as a guest machine.
• This virtual machine is managed by a software or
firmware, which is known as hypervisor or virtual
machine monitor (VMM).
Hypervisor
Types Of Hypervisor
• Type 1 ("bare metal“)
• Type 2 ("hosted")
Type 1
• The hypervisor runs directly on the underlying host
system.
• It does not require any base server operating system.
• It has direct access to hardware resources.
• Examples :VMware ESXi, Citrix XenServer, and Microsoft
Hyper-V hypervisor
• Advantages
• Faster -As they can directly communicate with hardware
resources
• Secure- if a single virtual machine crash, it does not affect
the rest of the guest operation system.
• generate less overhead
TYPE-2
• A Host operating system runs on the underlying host
system.
• Basically, the software is installed on an operating system.
Hypervisor asks the operating system to make hardware
calls.
• Example : VMware Player or Parallels Desktop, KVM,
Microsoft Hyper V, VMWare Fusion, Virtual Server 2005
R2, Windows Virtual PC and VMWare workstation 6.0.
• The type-2 hypervisor is very useful for engineers, and
security analysts (for checking malware, or malicious
source code and newly developed applications).
Virtualization
Virtual Machines (VMs):
▪ Abstraction of a physical host machine
▪ Resource (e.g. CPU, memory share),
▪ Software configuration (e.g. O/S, provided services).
▪ Hypervisor intercepts and emulates instructions from VMs, and
allows management of VMs,
▪ VMWare, Xen, etc.
App App App
OS OS OS
Hypervisor
Hardware
Virtualized Stack
Virtual Machines
• VM technology allows multiple virtual machines to run on
a single physical machine.
App App App App App
Xen
Guest OS Guest OS Guest OS
(Linux) (NetBSD) (Windows)
VMWare
VM VM VM
Virtual Machine Monitor (VMM) / Hypervisor
Denali
Hardware
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Virtualization in General
• Advantages of virtual machines:
▪ Run operating systems where the physical hardware is
unavailable,
▪ Easier to create new machines, backup machines, etc.,
▪ Software testing using “clean” installs of operating systems
and software,
▪ Emulate more machines than are physically available,
▪ Timeshare lightly loaded systems on one host,
▪ Debug problems (suspend and resume the problem
machine),
▪ Easy migration of virtual machines (shutdown needed or
not).
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Some Commercial Cloud Offerings
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Cloud Taxonomy
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The cloud computing architecture
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Cloud Computing Services Classification
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Infrastructure-as-a-Service
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The Platform-as-a-Service reference
model
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A taxonomy of virtualization techniques.
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User’s View of Virtualization
• SAN: Storage Area Network
• NAS: Network Attached Storage
Difference between Traditional Computer and
Virtual machines
Virtualization - Basics
• The ability to run multiple operating systems on a single
physical system and share the underlying hardware resources
• Virtualization can be viewed as utility computing, in which
computer processing power is seen as a utility that clients can
pay for only as needed.
• The usual goal of virtualization is to centralize administrative
tasks while improving scalability and work loads
Virtualization example
• Dividing your actual hard drive into different partitions.
• A partition is the logical division of a hard disk drive to create,
in effect, two or more separate hard drives C:, D:, E: etc..
Traditional App/Server
Virtualization - Definition
• It is "a technique for hiding the physical characteristics of
computing resources from the way in which other systems,
applications, or end users interact with those resources.
• This includes making a single physical resource (such as a
server, an operating system, an application, or storage device)
appear to function as multiple logical resources;
• OR - it can include making multiple physical resources (such
as storage devices or servers) appear as a single logical
resource."
Why Virtualization?
• Cost Reduction.
• Isolation and creating protected environment.
• Testing and evaluation of OS, kernel, or an
application.
• Ease of duplication.
• Relocation (and disaster recovery).
• Running Application not supported by the host.
• Green IT
Why Virtualization?
• The Reality:
✔ Most servers only use 5-15% of their capabilities on average, while
consuming 60-90% of their peak power
• The Solution – Virtualization
o Use one server to host multiple applications.
o Reduce energy consumption
o Reduce CO2 emissions
Running fewer, highly utilized servers
frees up space and power. Less space and
power is better for environment and saves
money.
Virtualization Benefits
• Reduce Real Estate Needs
• Increase Up Time
• Reduce CO2 Emissions, Power and Cooling Requirements
• Increase Flexibility
• Reduce Overall Costs
Virtualized Model - Cloud
Types of Virtualization
1) Hardware Virtualization
• When the virtual machine software or virtual machine
manager (VMM) is directly installed on the hardware
system is known as hardware virtualization.
• The main job of hypervisor is to control and monitoring the
processor, memory and other hardware resources.
• After virtualization of hardware system we can install
different operating system on it and run different
applications on those OS.
• Usage:
• Hardware virtualization is mainly done for the server
platforms, because controlling virtual machines is much
easier than controlling a physical server.
2) Operating System Virtualization
• When the virtual machine software or virtual machine
manager (VMM) is installed on the Host operating
system instead of directly on the hardware system is
known as operating system virtualization.
• Usage:
• Operating System Virtualization is mainly used for testing
the applications on different platforms of OS.
3) Server Virtualization
• It partition the resources of a server, which consist of
hardware, software and networking resources, and
distributing them over a network.
• When the virtual machine software or virtual machine
manager (VMM) is directly installed on the Server system is
known as server virtualization.
• virtual servers
• Usage:
• Server virtualization is done because a single physical
server can be divided into multiple servers on the demand
basis and for balancing the load.
4) Storage Virtualization
• Storage virtualization is the process of grouping the
physical storage from multiple network storage devices so
that it looks like a single storage device.
• gathering and merging multiple physical storage arrays and
presenting them as a single storage location to the user over
a network.
• It is employed typically by organizations and individuals
looking to scale and maintain their systems’ storage without
investing in physical storage devices.
• E.g. 2 TB disk drive (pooling several storage locations to
offer it)
Usage:
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• back-up and recovery purposes.
• It enables users to scale their storage capacity on-demand.
• It allows organizations to manage large amounts of crucial
data by allocating it to a single location.
• Backing up, recycling and dropping data is much easier
when consolidated at a single storage location.
• Virtualizing storage offers better storage performance at
significantly lesser expenses.
Desktop Virtualization
• It allows the users’ OS to be remotely stored on a server
in the data centre.
• It allows the user to access their desktop virtually, from
any location by a different machine.
• Users who want specific operating systems other than
Windows Server will need to have a virtual desktop.
• Benefits
▪ user mobility,
▪ portability,
▪ easy management of software installation, updates, and
patches.
Network Virtualization
• The ability to run multiple virtual networks with each has a
separate control and data plan.
• It co-exists together on top of one physical network.
• It can be managed by individual parties that is confidential to
each other.
• Network virtualization provides a facility to create virtual
networks—
▪ logical switches,
▪ routers,
▪ firewalls,
▪ load balancer,
▪ Virtual Private Network (VPN), and
▪ workload security within days or even in weeks.
Application Virtualization
• process of deploying a computer application over a network
(the cloud)
• It helps a user to have remote access of an application
from a server.
• The server stores all personal information and other
characteristics of the application but can still run on a
local workstation through the internet.
Advantages
• users can access a lots of applications in real-time without
having to allocate too much storage to all of them.
• Users can also run applications not supported by their devices’
operating systems.
• it eliminates the need for managing and updating several
applications across different operating systems for IT teams.
VM Taxonomy
Process VM
• These VMs are platforms created by operating system
specifically for the process.
• These VMs are created when the application is initiated
and they are destroyed when the application finishes
execution.
• These VM support binaries compiled on different
instruction set.
• Example: Java Virtual Machine.(JVM)
• The virtualizing software in the process VM environment
translates one instruction from one platform to another
platform.
• programs developed for variety of operating system or
with different instruction set architecture can be executed.
• These VMs terminates automatically once the process
terminates.
• “Platform independent”
System VM
• It is the VM that is generally created for virtualizing the
underlying hardware and networking resources.
• It provide a complete operational environment,
▪ guest operating system,
▪ user process,
▪ networking components,
▪ input output environment,
▪ graphical display components etc.
• These VMs are tied to the system and not any specific
process and will be running as long as the host hardware is
running or user terminates the VMs.
• have their own guest operating systems, which are made
bootable from OS template called images.
• VMM manages the allocation of, and access to, the
hardware resources of the host platform.
Primitive Operations in Virtual Machines
• A Multiplexing
• BS Suspension(Storage)
• C Provision(Resume) • D Life Migration
VM Multiplexing
• multiplexing =>the ability of using multiple instances.
• In a virtualized environment, applications are deployed in
VMs and hence restrictions regarding the number of VMs
that can be launched, type of application that can be run
in the VMs, the amount or share of the hardware that
can be consumed by these applications become irrelevant.
• Hence called VM multiplexing
VM Suspension
• It is the process of moving the virtual machines to a
paused state from running state.
• Any running or waiting VMs may be suspended from the
current state and moved to storage,
• The VMs reside in storage until revoked back to
execution.
VM Provisioning
• When needed, a suspended VM can be brought back to the
execution environment and be scheduled on the same
hardware or on a different hardware.
VM migration
• The VMs can be migrated directly from one server to
another server
▪ live migration without shutting down the virtual machines.
Moving a powered on virtual machine to a new host.(hot
migration)
▪ cold migration by shutting down the VMs and migrating the VM
and rebooting the VM at destination. Moving a powered off or
suspended virtual machine to a new host
Implementation Levels of Virtualization
• Hardware
▪ Server / OS / Devices ( peripheral devices like printer etc..)
▪ Desktop ( similar to above)
▪ Storage ( Memory, hard disk etc..)
▪ Network
• Application software
• Data
• FULL Virtualization
Virtualization Techniques
• Full Virtualization.
• OS-level Virtualization.
• Partial Virtualization (Historical, not used).
• Para-virtualization.
• Hardware -assested Virtualization.
• Para-virtualization
– VM does not simulate hardware
– Use special API that a modified guest OS must use
– Hypercalls trapped by the Hypervisor and serviced
– Xen, VMWare ESX Server
• OS-level virtualization
– OS allows multiple secure virtual servers to be run
– Guest OS is the same as the host OS, but appears isolated
– apps see an isolated OS
– Solaris Containers, BSD Jails, Linux Vserver
• Application level virtualization
– Application is gives its own copy of components that are not shared
– (E.g., own registry files, global objects)
– VE prevents conflicts
– JVM
Full Virtualization
• Full simulation of underlying hardware.
• Sharing a computer system among multiple users.
• Isolating users from each other (and from the control
program).
• The result is a system in which all software (including all
OS’s) capable of execution on the raw hardware can be run
in the virtual machine.
• Comprehensively simulate all computing elements as
instruction set, main memory, interrupts, exceptions, and
device access.
• Full virtualization is only possible given the right
combination of hardware and software elements.
The host OS emulated a hardware layer for each guest
OS.
Hardware-level virtualization-Server
• It is the masking of server resources (including the number
and identity of individual physical servers, processors, and
operating systems) from server users.
• The intention is to spare the user from having to understand
and manage complicated details of server resources while
increasing resource sharing and utilization and maintaining
the capacity to expand later.
• How dual boot is different ?
▪ In virtualization multiple OS run simultaneously
OS-Level Virtualization
• Concept: Same OS for everyone (host & guest), and isolation is
only in the user land.
• Pros: low overhead, highest performance.
• Cons: isolation, stability.
• Examples: FreeBSD Jails, Solaris Containers, Virtuzzo/Open
VZ.
Para virtualization
• Concept: A thin layer (called the hypervisor), interfaces the hardware to
all OS's (host and guest), Dom0 is called ”the privileged domain” which
can issue commands to the hypervisor.
• If Dom0 crashed (not the hypervisor), the guest OS still runs fine,
anyway you won't be able to control the hypervisor till you reboot.
Para virtualization
• Pros:
• Stability is very close to the hardware virtualization.
• Performance is very good (nothing can beat OS-level virtualization in
this matter).
• Overhead is very low (kernel level only, and not even a complete kernel).
• Cons:
• Not easy to implement (it's getting better these days).
• Both host and guest kernels has to be patched.
• Maintainability.
• Example: Xen
Hardware- assisted Virtualization
• Sometimes it's called accelerated virtualization or HVM (Hardware
Virtual Machines).
• Concept: Hardware provides support to run instructions independently
for each OS.
• Implémentation: IBM 370 (1972), Intel VT, AMD-V, UltraSparc, and
others.
• Exemples: linux KVM, Vmware fusion, M$ VirtualPC, Xen, Virtual Box.
Hardware- assisted Virtualization
• Pros:
• Highly reduces (theoretically eliminates) the
need to patch the guest OS.
• Theoretically optimal performance.
• Great Stability.
• Cons:
• Hardware restrictions.
Tools for Virtualization
• Amazon EC2 (Elastic Compute Generation 2)
• VMware – vSphere (Platform)
• Nimbus( Infrastructure as a service)
• Open Nebula( Flexible Enterprise Cloud)
• Eucalyptus( S/w for building Amazon Web
Services)
• O-virt (Free, Open source Virtualization
Platform, founded by Red Hat as a community
project)
Hypervisor
• Hypervisor runs above the supervisor mode.
• It runs in supervisor mode.
• It recreates a h/w environment.
• It is a piece of s/w that enables us to run one or more VMs on
a physical server(host).
• Two major types of hypervisor
• Type -I
• Type-II
Type-I Hypervisor
• It runs directly on top of the Type I Hypervisor
hardware.
• Takes place of OS.
• Directly interact with the ISA Windows Windows Linux Linux
exposed by the underlying virtual virtual virtual virtual
hardware. machine machine machine machine
• Also known as native virtual
machine
• Example: IBM CP/CMS
Para virtualization drivers and
hypervisor tools
Hypervisor (VMware vSphere, Citrix XenServer, Microsoft
Hyper-V
**ISA-Internet security and acceleration server Host – Physical hardware
**ABI-Application binary interface
Type-II Hypervisor
• It require the support of an
Type II Hypervisor
operating system to provide
virtualization services.
• Programs managed by the OS. Window Window Linux Linux
• Emulate the ISA of virtual h/w. s virtual s virtual virtual virtual
machine machine machine machine
• Also called hosted virtual
machine.
Para virtualization drivers and
tools
Hypervisor (Microsoft Virtual Server, VMware workstation)
Host – Operating system
** ISA-Internet security and acceleration server Host – Physical hardware
**ABI- Application binary interface
Virtual Machine Manager (VMM)
• Main Modules Interpreter
✔ Consists of interpreter routines
Dispatcher
✔ Executed whenever a VM executes a
✔ Entry Point of VMM privileged instruction.
✔ Reroutes the instructions issued by ✔ Trap is triggered and the corresponding
VM instance. routine is executed.
Allocator
✔ Deciding the system resources to be
provided to the VM.
✔ Invoked by dispatcher
Virtual Machine Manager (VMM)
VMM Architecture
SQL
Manageme
App Controller nt Console
Management
Server
Hosts (1000 Per Library
Management Server)
Criteria of VMM
• Equivalence – same behavior as when it is executed directly
on the physical host.
• Resource control – it should be in complete control of
virtualized resources.
• Efficiency – a statistically dominant fraction of the machine
instructions should be executed without intervention from the
VMM
