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Virtualization

Virtualization is the creation of substitutes for real resources – abstraction of real resources

Users/Applications are typically unaware of the substitution (layer of abstraction)

Examples:• computing systems/servers• network storage (e.g. SAN) • network resources (e.g. VLANs, VPNs,

HSRP - virtual ip address assignment).

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System (machine) Virtualization A virtual machine is a tightly isolated software

container that can run its own operating systems and applications as if it were a physical computer.

Was first introduced by IBM in the 60’s X86 virtualization introduced in the 90’s by

VMWare On a given h/w platform (host) – simulated

(virtual) machine environments are created Benefits:

• consolidation to reduce hw costs• workloads consolidation• single consolidated view/management• portability of virtual machines• can be used for testing/training

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System (machine) Virtualization

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Hypervisor functionality

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Virtualization approaches - Hosted• Hosted approach – host O/S runs virtualization

software, unmodified guest O/Ss run isolated from each other (separate virtual machines)

• Virtualization software is known as Type 2 hypervisor

• Additional resources are required for host O/S

• Example: Microsoft Virtual PC, VMWare Workstation

Hosted Architecture

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Virtualization approaches - Hypervisor

• Hypervisor (bare-metal or type 1) approach – there’s no host O/S. Virtual machines run on top of type 1 hypervisor directly on a hardware platform

• No resources are wasted for a Host O/S

• Higher virtualization efficiency can be achieved

• Example: VMWare ESX Server

Hypervisor or Bare-metal Architecture

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Paravirtualization

• Guest O/S is modified to include a call to hypervisor to access h/w resources

• Guest O/S is “aware” of running in a virtualized environment

• Makes the structure of hypervisor simpler• May make virtual machine more efficient• Can be a problem when Guest O/S can’t be

modified (proprietary O/S)

Paravirtualization

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HW Virtualization

• Virtualization on x86 machines was difficult to implement, involved a lot of overhead

• Starting in 2005 both Intel and AMD introduced processors enabled for virtualization – Intel VT and AMD-V Pacifica

• Both employ virtualization extensions to x86 architecture to allow more efficient virtualization

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X86 architecture – privilege levels

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Virtualization – ring de-privileging

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X86 architecture – with virtualization

Binary Translation

Paravirtualization

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X86 architecture – with HW- assisted virtualization

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Virtual machine networking

Virtual Embedded Bridge – a software switch as part of the hypervisor

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Virtual machine networking

External Hardware Switch – switching function performed by an external switch

Traditional Infrastructure

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Virtual Infrastructure

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