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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)
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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). 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 System (machine) Virtualization
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
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
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)
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
X86 architecture – with virtualization Paravirtualization Binary Translation
Virtual machine networking • Virtual Embedded Bridge – a software switch as part of the hypervisor
Virtual machine networking • External Hardware Switch – switching function performed by an external switch