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Virtualization and Cloud Computing

Lesson 27 of 30 in the free Cloud Computing notes on Siksha Sarovar, written by Rohit Jangra.

Virtualization and Cloud Computing

The Enabling Relationship

Cloud computing would not exist without virtualization. The defining characteristics of cloud services — on-demand self-service, broad network access, resource pooling, rapid elasticity, and measured service (the NIST SP 800-145 model) — are each directly enabled by specific virtualization capabilities.

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NIST Characteristics Mapped to Virtualization

NIST Cloud CharacteristicVirtualization CapabilityExample
On-Demand Self-ServiceVM provisioning via API (no human operator)AWS EC2 RunInstances API
Broad Network AccessVirtual NICs, SDN, overlay networksVPC with VXLAN tunnels
Resource PoolingMulti-tenancy via hypervisor isolationMultiple customer VMs on one host
Rapid ElasticityVM cloning, templates, live migrationAuto Scaling Groups on AWS
Measured ServiceHypervisor-level metering per VMPer-vCPU-hour billing

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Multi-Tenancy

A single physical server hosts dozens of customer VMs simultaneously. The hypervisor enforces strict isolation so Tenant A cannot access Tenant B's memory, storage, or network traffic. This multi-tenancy model is the economic foundation of public cloud — the provider achieves high utilization while customers receive the illusion of dedicated hardware.

Elasticity

Virtual machines can be:

  • Cloned from golden images in seconds.
  • Scaled up (adding vCPUs/RAM) with minimal downtime on modern hypervisors.
  • Migrated live between physical hosts (vMotion, XenMotion, KVM live migration) for load balancing without service interruption.
  • Terminated immediately, returning resources to the pool.

This elasticity is impossible with physical-only infrastructure where provisioning a new server takes hours or days.

Resource Pooling

The hypervisor presents a logical resource pool above physical hardware. CPU cycles, RAM pages, and disk IOPS are allocated dynamically. Technologies like VMware's Distributed Resource Scheduler (DRS) continuously rebalance VMs across hosts to maximize utilization.

Live Migration

Physical → Virtualization Layer → Cloud Services

Key Takeaway

Virtualization is the infrastructure substrate of cloud computing. Every API call to spin up a server, every auto-scaling event, every snapshot backup, and every per-second billing calculation is rooted in what the hypervisor layer makes possible. Studying cloud without virtualization is like studying a building without understanding its foundation.