CLOUD COMPUTING

• On demand provision of computational resources (Infrastructure,

Platform, Software).
• Requires high availability of resources and optimum use.
• Virtualization is the enabling technology and creates virtual machines
that allows a single machine to act as if it were many machines.
• Benefits of virtualization for cloud computing: Reduces capital expenses
and maintenance costs through server consolidation, reduces physical
space needed in data centers. Resource Management, Migration,
Maintainability, High availability and Fault tolerance are other benefits.
• Virtualization is implemented using hypervisors.

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 VIRTUALIZATION
Machine Stack showing
virtualization opportunities • Creation of a virtual version of hardware
using software.
Application • Runs several applications at the same time
on a single physical server by hosting each
of them inside their own virtual machine.

Libraries • By running multiple virtual machines

simultaneously, a physical server can be
utilized efficiently.

Operating Primary approaches to virtualization

System • Platform virtualization Ex : Server
• Resources virtualization Ex : Storage,
Network
Hardware

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 HYPERVISOR
• Hypervisor plays an important role in the virtualization scenario by virtualization of
hardware. It provides support for running multiple operating systems concurrently
in virtual servers created within a physical server.

• The virtualization layer is the software responsible for hosting and managing all
VMs. The virtualization layer is a hypervisor running directly on the hardware.

• Example: VMWare, Xen, KVM.

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 SERVER WITHOUT VIRTUALIZATION

• Only one OS can run at a time

within a server.
• Under utilization of resources.
Multiple Software
Applications
• Inflexible and costly infrastructure.
• Hardware changes require manual
effort and access to the physical
Operating System server.
Hardware

CPU Memory NIC

DISK

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 SERVER WITH VIRTUALIZATION

• Can run multiple OS

Multiple Software Multiple Software simultaneously.
Applications Applications
• Each OS can have different
Operating System Operating System hardware configuration.
Virtual Server 1 Virtual Server 2 • Efficient utilization of hardware
resources.
Hypervisor • Each virtual machine is
independent.
Hardware
• Save electricity, initial cost to buy
servers, space etc.
• Easy to manage and monitor
CPU Memory NIC DISK virtual machines centrally.

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 HYPERVISOR TYPE

Full virtualization
Multiple Software
Applications
Multiple Software
Applications • Enables hypervisors to run an
unmodified guest operating
Operating System Operating System system (e.g. Windows 2003 or
Virtual Server 1 Virtual Server 2 XP).
• Guest OS is not aware that it is
Hypervisor being virtualized.

Hardware
• E.g.: VMware uses a
combination of direct execution
and binary translation techniques
to achieve full virtualization of
CPU Memory NIC DISK server systems.

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 HYPERVISOR TYPE

Multiple Software Multiple Software Para virtualization

Applications Applications
• Involves explicitly modifying
Para virtualized Guest Para virtualized Guest guest operating system (e.g.
Operating System Operating System
SUSE Linux Enterprise Server
Virtual Server 1 Virtual Server 2
11) so that it is aware of being
virtualized to allow near native
Hypervisor / VMM performance.
Hardware • Improves performance.
• Lower overhead.
• E.g.: Xen supports both
Hardware Assisted Virtualization
(HVM) and Para-Virtualization
CPU Memory NIC DISK
(PV).

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 HYPERVISOR IMPLEMENTATION
APPROACHES
Bare metal Approach
VM VM VM • Type I Hypervisor.
• Runs directly on the system hardware.
• May require hardware assisted
virtualization technology support by
the CPU.
Hypervisor • Limited set of hardware drivers
provided by the hypervisor vendor.
Kernel Driver • E.g.: Xen, VMWare ESXi

Hardware

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 HYPERVISOR IMPLEMENTATION
APPROACHES
Hosted Approach
VM VM • Type II Hypervisor.
• Runs virtual machines on top of a
Applications host OS (windows, Unix etc.)
Hypervisor • Relies on host OS for physical
resource management.
• Host operating system provides
drivers for communicating with the
server hardware.
Host Operating System
• E.g.: VirtualBox

Hardware

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 VMWARE ESXI
• Bare Metal Approach.

• Full virtualization.

• Proven technology.
VM VM VM
• Used for secure and robust

virtualization solutions for

Hypervisor virtual data centers and cloud

infrastructures.

Hardware • Takes advantage of support

for hardware assisted

Architecture of VMWare ESXi virtualization for 64-bit OS on

Intel processors. 10
 CITRIX XEN SERVER
• Open source; bare metal.
• Offers both Hardware Assisted
Virtualization (HVM) and Para-
Domain
Zero
Virtualization (PV)
VM VM
Guest • Needs virtualization support in
the CPU for HVM.
• Xen loads an initial OS which
Hypervisor runs as a privileged guest called
“domain 0”.
• The domain 0 OS, typically a
Linux or UNIX variant, can talk
Hardware
directly to the system hardware
(whereas the other guests
cannot) and also talk directly to
the hypervisor itself. It allocates
Architecture of Xen
and maps hardware resources
for other guest domains.
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 UBUNTU KVM

• Kernel based virtual machine

(Kernel Based VM)
1. Linux Applications
2. KVM Management • Open source.
Console VM VM • Kernel-level extension to Linux.
• Full virtualization.
Linux • Supports full virtualization and
KVM hence does not need hardware
Linux Kernel
assisted virtualization support
in the CPU.

Hardware

Architecture of KVM

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