Virtualization

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Virtualization

• What is virtualization?
• Why virtualize?
• Virtualization architectures
• How virtualization affects networking
• Virtual infrastructure and how it fits into Cloud
  computing

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What is 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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Virtualization lifecycle
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System/Server 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.
• An old idea was first introduced by IBM in the
  60s
• X86 virtualization introduced in the 90s by
  VMWare
• On a given h/w platform simulated (virtual)
  physical machines are created
• Can boot/run multiple instances of different OS
  on the same physical machine

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Why virtualization?

• Workloads consolidation to reduce hw costs-
  todays powerful hw can support multiple VMs
• Single consolidated view/management of VMs
• Portability of virtual machines-can migrate VMs
  from one machine to another without shutting down
• Isolation VMs are protected from each other and
  from hw resources
• Can be used for testing/training/software
  development- run multiple Oss simultaneously
• ISP hosts/Cloud computer provides can divide a
  single physical machine to different customers

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System (Server) 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

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Hosted Architecture
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Virtualization approaches - Hypervisor

• Hypervisor (bare-metal or type 1) approach
  theres 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

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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 cant be modified
  (proprietary O/S)

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X86 architecture privilege levels
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Virtualization ring de-privileging
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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 with virtualization
Paravirtualization
Binary Translation
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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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Traditional Infrastructure
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Virtual Infrastructure