CC-5 - MOD.pptx Cloud Vertulization nand

CLOUD COMPUTING
Cloud Virtualization and Clustering - II Courtesy:
Dr Gnanasekaran
Thangavel

11/19/2024 2
Implementation Levels of Virtualization
Virtualization technology benefits the computer and IT industries by enabling users to share
expensive hardware resources by multiplexing VMs on the same set of hardware hosts.
Virtual workspaces:
– An abstraction of an execution environment that can be made dynamically available to authorized
clients by using well-defined protocols,
– Resource quota (e.g. CPU, memory share),
– Software configuration (e.g. O/S, provided services).
• Implement on Virtual Machines (VMs):
– Abstraction of a physical host machine,
– Hypervisor intercepts and emulates instructions
from VMs and allows management of VMs.
– VMWare, Xen, etc.
• Provide infrastructure API:
– Plug-ins to hardware/support structures
Hardware
OS
App App App
Hypervisor
OS OS
Virtualized Stack

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Virtual Machines
• VM technology allows multiple virtual machines to run on
a single physical machine.
Hardware
Virtual Machine Monitor (VMM) / Hypervisor
Guest OS
(Linux)
Guest OS
(NetBSD)
Guest OS
(Windows)
VM VM VM
App
App App
App
App
Xen
VMWare
UML
Denali
etc.
Performance: Para-virtualization (e.g. Xen) is very close to raw physical performance!

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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).
– Run legacy systems!

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What is the purpose and benefits?
• Cloud computing enables companies and applications, which are system
infrastructure dependent, to be infrastructure-less.
• By using the Cloud infrastructure on “pay as used and on demand”, all of us
can save in capital and operational investment!
• Clients can:
– Put their data on the platform instead of on their own desktop PCs and/or on their own
servers.
– They can put their applications on the cloud and use the servers within the cloud to do
processing and data manipulations etc.
– In computing, virtualization means to create a virtual version of a device
or resource, such as a server, storage device, network or even an
operating system where the framework divides the resource into one or
more execution environments.

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Difference between Traditional and Virtual machines
• A traditional computer runs with a host operating system specially tailored for its hardware
architecture
• After virtualization, different user applications managed by their own operating systems (guest
OS) can run on the same hardware, independent of the host OS.
• The Virtualization layer is the middleware between the underlying hardware and virtual machines
represented in the system, also known as virtual machine monitor (VMM) or hypervisor.
With sufficient storage,
any computer platform can
be installed in another
host computer, even if
they use processors with
different instruction sets
and run with distinct
operating systems on the
same hardware.

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Virtualization Layers
The virtualization software creates the abstraction of VMs by
interposing a virtualization layer at various levels of a
computer system.
Common virtualization layers include:
1. the instruction set architecture (ISA) level,
2. hardware level,
3. operating system level,
4. library support level, and
5. application level

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Virtualization Ranging from Hardware to Applications in Five Abstraction Levels

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1.Virtualization at Instruction Set Architecture (ISA) level:
• At the ISA level, virtualization is performed by emulating a given ISA by the ISA of the host machine.
Instruction set emulation leads to virtual ISAs created on any hardware machine. e.g, MIPS binary code
can run on an x-86-based host machine with the help of ISA emulation.
• With this approach, it is possible to run a large amount of legacy binary code written for various
processors on any given new hardware host machine.
• code interpretation – dynamic binary translation - virtual instruction set architecture (V-ISA)
• Advantage:
• It can run a large amount of legacy binary codes written for various processors on any given new
hardware host machines
• best application flexibility
• Shortcoming & limitation:
• One source instruction may require tens or hundreds of native target instructions to perform its
function, which is relatively slow.
• V-ISA requires adding a processor-specific software translation layer in the complier.

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2.Virtualization at Hardware Abstraction level:
• Hardware-level virtualization is performed right on top of the bare hardware.
• On the one hand, this approach generates a virtual hardware environment for a VM.
• On the other hand, the process manages the underlying hardware through
virtualization.
• The idea is to virtualize a computer’s resources, such as its processors, memory
and I/O devices. The intention is to upgrade the hardware utilization rate by multiple
users concurrently.
Advantage:
• Has higher performance and good application isolation
Shortcoming & limitation:
• Very expensive to implement (complexity)

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3.Virtualization at Operating System (OS) level:
• OS-level virtualization creates isolated containers on a single physical server
and the OS instances to utilize the hardware and software in data centers. The
containers behave like real servers.
• OS-level virtualization is commonly used in creating virtual hosting environments
to allocate hardware resources among a large number of mutually distrusting
users.
Advantage:
• Has minimal startup/shutdown cost, low resource requirement, and high
scalability; synchronize VM and host state changes.
• All VMs at the operating system level must have the same kind of guest OS
• Poor application flexibility and isolation.

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Virtualization at OS Level

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Advantages of OS Extension for Virtualization
1. VMs at OS level has minimum startup/shutdown costs
2. OS-level VM can easily synchronize with its environment
Disadvantage of OS Extension for Virtualization
•All VMs in the same OS container must have the same or similar
guest OS, which restrict application flexibility of different VMs on the
same physical machine.

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4.Library Support level:
• Since most systems provide well-documented APIs, such an interface becomes
another candidate for virtualization.
• Virtualization with library interfaces is possible by controlling the communication
link between applications and the rest of a system through API hooks.
• The software tool WINE has implemented this approach to support Windows
applications on top of UNIX hosts.
• Another example is the vCUDA which allows applications executing within VMs
to leverage GPU hardware acceleration.
Advantage:
• It has very low implementation effort
• poor application flexibility and isolation

11/19/2024 15
5.User-Application Level
• Virtualization at the application level virtualizes an application as a VM. On a traditional OS, an
application often runs as a process.
• Therefore, application-level virtualization is also known as process-level virtualization.
• The most popular approach is to deploy high level language (HLL) VMs. In this scenario, the
virtualization layer sits as an application program on top of the operating system, and the layer
exports an abstraction of a VM that can run programs written and compiled to a particular
abstract machine definition.
• Other forms of application-level virtualization are known as application isolation, application
sandboxing, or application streaming.
Advantage:
• has the best application isolation
• low performance, low application flexibility and high implementation complexity.

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User-Application Level Virtualization

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Hypervisor
• A hypervisor is a hardware virtualization technique allowing multiple operating systems,
called guests to run on a host machine. This is also called the Virtual Machine Monitor
(VMM).
Type 1: bare metal hypervisor
• sits on the bare metal computer hardware like the CPU, memory, etc.
• All guest operating systems are a layer above the hypervisor.
• The original CP/CMS hypervisor developed by IBM was of this kind.
Type 2: hosted hypervisor
• Run over a host operating system.
• Hypervisor is the second layer over the hardware.
• Guest operating systems run a layer over the hypervisor.
• The OS is usually unaware of the virtualization

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Full Binary Translation and Host-based Virtualization
• Depending on implementation technologies, hardware virtualization VM
architectures can be classified into two categories:
– Full virtualization and
– Host-based virtualization.
• Full virtualization does not need to modify the host OS. It relies on
binary translation to trap and to virtualize the execution of certain
sensitive, non virtualizable instructions.
• In a host-based system, both a host OS and a guest OS are used. A
virtualization software layer is built between the host OS and guest OS.
• These two classes of VM architecture are introduced next.

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Binary Translation of Guest OS Requests Using a VMM
• This approach was implemented by
VMware and many other software
companies.
• VMware puts the VMM at Ring 0 and the
guest OS at Ring 1. The VMM scans the
instruction stream and identified the
privileged, control- and behavior sensitive
instructions.
• When these instructions are identified, they
are trapped into the VMM, which emulates
the behavior of these instructions.
• The method used in this emulation is called
binary translation. Therefore, full
virtualization combines binary translation
and direct execution.

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Host-Based Virtualization
• An alternative VM architecture is to install a virtualization
layer on top of the host OS. This host OS is still responsible
for managing the hardware.
• This host-based architecture has some distinct advantages.
First, the user can install this VM architecture without
modifying the host OS. The virtualizing software can rely on
the host OS to provide device drivers and other low-level
services. This will simplify the VM design and ease its
deployment.
• Second, the host-based approach appeals to many host
machine configurations. Compared to the hypervisor/VMM
architecture, the performance of the host-based architecture
may also be low.

11/19/2024 21
Para-virtualization
• Para-virtualization needs to
modify the guest operating
systems.
• A para-virtualized VM
provides special APIs
requiring substantial OS
modifications in user
applications.
• Performance degradation is a
critical issue of a virtualized
system.

11/19/2024 22
Full Virtualization vs. Para-Virtualization
Full virtualization
• Does not need to modify guest OS, and critical instructions are emulated by
software through the use of binary translation.
• VMware Workstation applies full virtualization, which uses binary translation to
automatically modify x86 software on-the-fly to replace critical instructions.
Advantage: no need to modify OS.
Disadvantage: binary translation slows down the performance.
Para virtualization
• Reduces the overhead, but cost of maintaining a paravirtualized OS is high.
• The improvement depends on the workload.
• Para virtualization must modify guest OS, non-virtualizable instructions are
replaced by hyper calls that communicate directly with the hypervisor or VMM.
• Para virtualization is supported by Xen, Denali and VMware ESX.

CC-5 - MOD.pptx Cloud Vertulization nand

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