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Definition
It is the technology which is making a
transformation in IT by saving cost, energy,
time.
Virtualization provides an emulation of
hardware (computer resources) to
different virtual machines. A virtual
machine is an illusion of existing machine,
which uses the resources of underlying
machine & works as actual machine.
Virtualization is to run different operation
systems and different applications on
same machine at the same time, giving
an illusion that each is running on different
machines.
One physical machine to support multiple
virtual machines that run in parallel.
Need for Virtualization
Single OS image per
machine
Software and hardware
tightly coupled
Running multiple
applications on same
machine often creates
conflict
Inflexible and costly
infrastructure
Need… Cloud computing promises to give you as
much as you desire. It is a fully scalable
and elastic model. But to fulfill the real
time demands a lot of infrastructure is
required, which would require a lot of cost
and energy consumption too. The solution
to it is Virtualization. As with virtualization
the same resource can be made
available to many user concurrently.
Therefore virtualization is the basic need
of cloud computing
Virtualization Gave..
Hardware-independence ofoperating system andapplications
Virtual machines can beprovisioned to any system
Can manage OS andapplication as a single unitby encapsulating them intovirtual Machines
Benefits of Virtualization
Reduce the number of physical machines
Isolate environments but share hardware
Make better use of existing capacity
Virtualize Network and SAN interfaces toreduce infrastructure needs
Ultimately save on maintenance
More Flexible
Energy Saving
…
Execution This type of virtualization provides an
execution environment for executing theapplications /operating system/ byte code.
It can be achieved by:
Hardware Level Virtualization: - This type ofvirtualization provides an illusion of havingmany resources (hardware) over onemachine (hardware). Same hardware isemulated (reproduced) to many users. Samehardware can be used as different hardware.
Hardware Virtualization
For it a Virtual Machine Manager (VMM) is
required, which is called hypervisor. A
hypervisor is one, which receives the
request from created Virtual Machine for
a resource and allocates the resource
from underlying hardware.
Hypervisor
A computing layer which allows multiple
operating systems to run on a host computer at
the same time.
Originally developed in the 1970s as part of the
IBM S/360
Also known as VMM (Virtual Machine Monitor)
The Hypervisor
The role of the Hypervisor in supporting Guest
Operating Systems on a single machine.
In it the complete hardware is emulated
by VMM to create different Virtual
machines. These Virtual machines can
have different operation system if desired.
Thus, actually (physically) there is only one
machine with one operating system but it
appears as if there are many machines
with different operation system.
Application shares the resources & run
concurrently as if running on different
machines.
Types of Hypervisor
Two Types
Type1:Bare Metal,Native (Hosted without
host O/S)
Type2: (Hosted on Host O/S)
Hardware Virtualization Types Full virtualization:- This allow running an application /
operation system or virtual machine, in the same way as itwould have run on host, without any modification in thecode. It provides complete isolation.
Para virtualization:- In it the guests need to be modified. Theoperation system to be put on virtual machine need somemodifications, this they are generally used for open sourceoperation system. It is aimed to demand execution of someperformance critical operation directly on the host.
Partial Virtualization:- It provides partial emulation ofunderlying hardware, thus the complete hardware(resources) are not virtualized, only some part is virtualized.It results not complete isolation of guest operation system.Many application can run transparently, but not all thefeatures of operation system be supported.
KEY FEATURES
.Partitioning
.Different OS can run on one physical machine
.System resources can be divided between virtual machines
•Isolation
Fault and security isolation on a hardware level
Extended resource control for constant performance
•Encapsulation
Complete status of a virtual machine can be stored in a file
Move and copy of a virtual machine is as easy as it is with files
VMWARE VMOTION
The VMotion technology allows the live migration of virtual machines
from one physical server to another and needs therefore no downtime for
maintenance activities.
Move running applications to other servers without disruption. Zero downtime for
hardware maintenance.
Automates moving virtual machines to other hosts and automates re-balancing
after maintenance complete
Operation System virtualization
In it the same operation system, providesdifferent execution environment for differentconcurrent applications. There is nohypervisor, all the application runs on samemachines having one operation system.Different applications share the resources andrun concurrently as if running on differentmachines. A separate user space instance iscreated. This is provided by time-sharingoperation system like UNIX. Different userspace is provided to all users
Programming Level Virtualization
In it the code of program is complied for a
Virtual machine not for machine code eg.
Java.
Application Level Virtualization
Application Level Virtualization allows applicationto be run on run time environment, which nativelydo not support all the features required by suchapplication. It allows running application on oneoperating system, which actually does not supportthat application. It allows executing a program,compiled for different network. This is done atoperating system level by emulation, using a thinlog on program or operating system componentseg. Cross over provides facility to run windowsapplication on Mac operating system.
Storage
In this type of virtualization basic focus is
on storage of the data. User can have
access to unlimited amount of storage
without even worrying about their actual
location. Data is accessed by logical
address or path. Google drive, Drop-box
are examples of this category
Network
It can be grouped in two categories. Internal
and External. In External Network Virtualization
a virtual LAN (VLAN) is created, it gives
capability of real network. It is a combination
of Hardware appliances and some soft-wares
for network virtualization. The groups of hosts
make a VLAN that communicate with each
other as if they are in real LAN. In Internal
Network Virtualization, network facility is
provided by Operating System.