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Virtualization Agility and VM Migration

Virtualization Agility and VM Migration

Definition

Agility is the ability to create and change execution environments through software. VM migration moves a virtual machine to another physical host; live migration supports this while the VM is running.

Lecture capabilities

  • Pause and restart OS execution.
  • Migrate VMs to consolidate workloads or move work away from overloaded hosts.
  • Duplicate VMs and rapidly spawn instances.
  • Support disaster recovery.
  • Change infrastructure dynamically using code or interface actions.

The professor emphasizes agility as a particularly important benefit. Autonomic systems need infrastructure that can act on decisions; AI may help choose a response, but does not itself supply the infrastructure’s ability to reconfigure.

Study example

During a quiet period, move VMs from three lightly loaded hosts onto two, then reduce the power state of the empty host. When demand rises, bring capacity back and redistribute work.

Important rules and clarifications

  • Migration changes placement; it does not by itself add workload capacity.
  • Duplication can create an extra instance, but application state, requests, and data must be handled correctly before that instance helps serve demand.
  • Disaster recovery needs recoverable state and a recovery process; virtualization supplies useful mechanisms rather than automatically guaranteeing recovery.
  • Live migration should not be interpreted as an unconditional promise of zero interruption under every implementation or workload.

Common mistakes

  • Reducing agility to savings on hardware purchases.
  • Assuming every application scales merely because its VM is copied.
  • Confusing moving a VM with distributing the application across several VMs.

Source

Fulvio Risso, Introduction to Computing Virtualization, slides 14-15. Lecture context: Lecture 02 - Introduction to Computing Virtualization. The example and operational qualifications are study explanations; migration internals are not covered in these slides.

Expansion in Lecture 03

VM Migration - Cold Hot and Live develops the three migration categories, execution state, disks, dirty pages, and network reachability from Lecture 03 - Computing Virtualization Technologies and Tools, PDF pages 101-107 (printed slides 107-113). Keep this note for the motivation and use the detailed note for migration mechanisms.

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