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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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