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Unit 1 of 4 · M.Sc IT Sem 3

Unit 1: Cloud fundamentals and migration

Cloud Computing notes · PTU syllabus (PGCA1937)

3 min read10 topics10 exam questions
On this page
  1. Unit summary
  2. Computing trends leading to the cloud
  3. The cloud vision and reference model
  4. Service and deployment models
  5. Characteristics, benefits and challenges
  6. Cloud vs cluster vs grid computing
  7. Migrating into a cloud: approaches
  8. The seven-step migration model
  9. Virtualisation: characteristics and taxonomy
  10. Xen, VMware and Hyper-V
  11. Capacity planning and scaling
  12. Key terms
  13. Quick revision
  14. Important questions

Unit summary

Cloud computing delivers computing as a utility. This unit covers trends from grid, cluster, distributed and utility computing to the cloud, the cloud vision and reference model, deployment models, characteristics, benefits and challenges, cloud versus cluster and grid computing, migrating into the cloud with the seven-step model, virtualisation and its taxonomy, Xen, VMware and Hyper-V, and capacity planning and scaling.

After this unit you can

  • Trace the evolution of cloud computing and describe its reference model
  • Explain characteristics, deployment models, benefits and challenges
  • Plan cloud migration
  • Explain virtualisation, hypervisors, capacity planning and scaling

PTU syllabus topics

  • Grid/cluster/distributed/utility/cloud computing trends
  • cloud vision
  • reference model
  • deployment models
  • characteristics
  • benefits and challenges
  • cloud vs cluster vs grid computing
  • migrating into a cloud (approaches, seven-step model)
  • virtualization characteristics and taxonomy
  • Xen/VMware/Hyper-V
  • capacity planning and scaling
HierarchyCloud service models
  1. SaaS

    Ready software: Gmail, Salesforce

  2. PaaS

    Platform to build apps: App Engine

  3. IaaS

    Virtual machines, storage, networks: AWS EC2

1

Topic 1

Computing trends leading to the cloud

ComparisonComputing paradigms
Idea
Example

Distributed computing

Many networked computers cooperate on a task and appear as one system

Web search back ends

Cluster computing

Tightly coupled, homogeneous computers in one location acting as a single system

University HPC clusters

Grid computing

Loosely coupled, heterogeneous resources from different organisations shared for large tasks

CERN's Worldwide LHC Computing Grid

Utility computing

Computing resources metered and paid for like electricity

Pay-per-use servers

Cloud computing

On-demand, elastic, self-service resources over the internet, combining virtualisation and utility pricing

AWS, Azure, Google Cloud

2

Topic 2

The cloud vision and reference model

  • Vision: computing as the fifth utility — users obtain applications, platforms and infrastructure on demand from anywhere, paying only for what they use, without owning hardware.
HierarchyCloud reference model
  1. SaaS

    Applications delivered over the web — email, CRM, office suites

  2. PaaS

    Runtime platforms, databases and development tools

  3. IaaS

    Virtual machines, storage, networks

  4. Virtualisation and management layer

    Hypervisors, orchestration, monitoring, billing

  5. Physical infrastructure

    Data centres, servers, storage, networking

Key termsNIST reference roles
Cloud consumer
Uses services
Cloud provider
Makes services available
Cloud carrier
Provides connectivity
Cloud broker
Manages, integrates or aggregates services
Cloud auditor
Independently assesses security, privacy and performance
3

Topic 3

Service and deployment models

Cloud computing delivers computing resources — servers, storage, software — over the internet on a pay-as-you-use basis.

Service modelWhat the provider suppliesExamples
SaaS (software as a service)Ready-to-use applicationsMicrosoft 365, Google Workspace, Zoho Books, Salesforce
PaaS (platform as a service)Platform to build and run appsGoogle App Engine, Azure App Service
IaaS (infrastructure as a service)Virtual servers, storage, networksAWS EC2, Microsoft Azure VMs
  • Deployment models: public, private, hybrid and community cloud.
  • Benefits: low upfront cost, scalability, anywhere access, automatic updates, collaboration. Risks: dependence on internet, data privacy, vendor lock-in.
ComparisonDeployment models
Who uses
Trade-off

Public cloud

Many customers share provider infrastructure

Low cost, scalable; less control

Private cloud

One organisation, on-premises or hosted

More control and compliance; costlier

Hybrid cloud

Mix of public and private with integration

Flexibility; complex to manage

Community cloud

Organisations with shared needs (government)

Shared cost; limited scale

  • India: MeghRaj (GI Cloud) for government; data localisation requirements for payments data (RBI).
4

Topic 4

Characteristics, benefits and challenges

Key termsEssential characteristics (NIST)
On-demand self-service
Provision resources without human interaction
Broad network access
Use from any device over the network
Resource pooling
Multi-tenant sharing of resources
Rapid elasticity
Scale up and down quickly
Measured service
Usage metered and billed
ComparisonBenefits and challenges
Benefits
Challenges

Cost

No capital expense; pay as you go

Unpredictable bills without governance

Agility

Resources in minutes

Skills gap

Scale and reliability

Global regions, redundancy

Outages of a provider affect many customers

Control

Provider handles maintenance

Vendor lock-in, data location and compliance, security and privacy, latency

5

Topic 5

Cloud vs cluster vs grid computing

ComparisonComputing architectures
Structure
Typical use

Client–server

Clients request services from dedicated servers

Enterprise applications, databases

Peer-to-peer

Nodes share resources directly without a central server

File sharing, blockchain

Grid computing

Distributed computers pool resources for large tasks

Scientific computing

Cloud computing

On-demand, elastic, metered resources from a provider over the internet

Almost all modern IT

  • NIST characteristics of cloud: on-demand self-service, broad network access, resource pooling, rapid elasticity, measured service.
ComparisonCloud, cluster and grid
Cluster and grid
Cloud

Ownership

Owned by one organisation (cluster) or a collaboration (grid)

Owned by a provider; rented by many

Resources

Fixed; jobs queued

Elastic, on demand

Access

Batch job schedulers

Self-service portals and APIs

Billing

Usually free to members

Metered pay-per-use

6

Topic 6

Migrating into a cloud: approaches

ClassificationThe 6 Rs of migration
Migration strategies

  • Rehost

    Lift and shift as is

  • Replatform

    Lift, tinker and shift — minor optimisation

  • Refactor (re-architect)

    Redesign as cloud-native

  • Repurchase

    Move to SaaS

  • Retire

    Switch off unneeded systems

  • Retain

    Keep on-premises for now

7

Topic 7

The seven-step migration model

ProcessSeven-step cloud migration model
  1. 1

    Assessment

    Business case, costs, readiness

  2. 2

    Isolation

    Identify dependencies of applications

  3. 3

    Mapping

    Map components to cloud services

  4. 4

    Re-architect

    Redesign parts that need change

  5. 5

    Augmentation

    Use cloud features to improve the application

  6. 6

    Testing

    Validate functionality and performance

  7. 7

    Optimisation

    Tune cost, performance and security after migration

8

Topic 8

Virtualisation: characteristics and taxonomy

  • Virtualisation creates virtual versions of hardware, operating systems, storage or networks, so many isolated environments share one physical machine.
Key termsCharacteristics of virtualised environments
Increased security
Isolation between guests
Managed execution
Sharing, aggregation, emulation and isolation of resources
Portability
Virtual machine images move between hosts
Consolidation
Higher utilisation of servers
ClassificationTaxonomy of virtualisation
Virtualisation

  • Execution virtualisation

    Hardware-level (hypervisors: full, para- and hardware-assisted) and process-level (application VMs such as the JVM)

  • Storage virtualisation

    Pooling disks into virtual volumes (SAN, software-defined storage)

  • Network virtualisation

    VLANs, virtual switches, software-defined networking

  • Desktop and application virtualisation

    Virtual desktops (VDI), streamed applications

  • Containers

    OS-level virtualisation sharing one kernel — Docker, Kubernetes

ComparisonHypervisor types
Type 1 (bare metal)
Type 2 (hosted)

Runs on

Directly on hardware

On a host operating system

Performance

High

Lower

Examples

VMware ESXi, Microsoft Hyper-V, Xen, KVM

VirtualBox, VMware Workstation

9

Topic 9

Xen, VMware and Hyper-V

ComparisonHypervisor case studies
Architecture
Notes

Xen

Type 1 microkernel hypervisor; privileged Dom0 manages unprivileged DomU guests; pioneered paravirtualisation (modified guest OS) and also supports hardware-assisted full virtualisation

Open source; used by early AWS EC2 and Citrix Hypervisor

VMware

ESXi bare-metal hypervisor; full virtualisation using binary translation and hardware assistance; vCenter for management, vMotion for live migration

Market leader in enterprise data centres

Microsoft Hyper-V

Type 1 hypervisor with a parent partition running Windows and child partitions for guests; enlightened guests use VMBus for fast I/O

Integrated with Windows Server and Azure

10

Topic 10

Capacity planning and scaling

  • Capacity planning estimates the resources needed to meet expected demand at an acceptable service level and cost.
ProcessCapacity planning process
  1. 1Measure current load and baseline performance
  2. 2Forecast demand (growth, seasonal peaks)
  3. 3Model resource needs and identify bottlenecks
  4. 4Choose a scaling strategy
  5. 5Monitor and adjust
ComparisonScaling approaches
Vertical scaling (scale up)
Horizontal scaling (scale out)

Method

Bigger machine — more CPU or RAM

More machines behind a load balancer

Limit

Hardware ceiling; downtime to resize

Nearly unlimited; app must be stateless or share state

Cloud feature

Change instance size

Auto-scaling groups add or remove instances by metrics

Example

An admission portal normally runs on 2 servers; during result week traffic rises tenfold. Auto-scaling with a rule "add a server when average CPU exceeds 70%" grows the pool to 15 servers and shrinks it afterwards, so the college pays only for the peak days.

Key terms

Grid computing
Sharing heterogeneous resources across organisations
Utility computing
Metered, pay-per-use computing
Elasticity
Ability to scale resources up and down on demand
Hypervisor
Software that creates and runs virtual machines
Paravirtualisation
Guest OS modified to cooperate with the hypervisor

Quick revision

  • Distributed, cluster, grid, utility, cloud.
  • Vision; reference model layers; NIST roles.
  • SaaS, PaaS, IaaS; public, private, hybrid, community; NIST characteristics; benefits and challenges.
  • 6 Rs; seven-step migration model.
  • Virtualisation characteristics and taxonomy; Type 1 and 2 hypervisors; Xen, VMware, Hyper-V; capacity planning; vertical and horizontal scaling.

Important exam questions

Practice questions written to the PTU exam pattern for this unit's syllabus: short answers (Section A style) and long answers (Sections B and C style).

Short-answer questions

  1. Q1.Distinguish cluster and grid computing.
  2. Q2.What is utility computing?
  3. Q3.Name the five NIST characteristics of cloud computing.
  4. Q4.What is the seven-step migration model?
  5. Q5.Distinguish full virtualisation and paravirtualisation.
  6. Q6.Distinguish vertical and horizontal scaling.

Long-answer questions

  1. Q1.Explain the evolution of computing paradigms leading to cloud computing.
  2. Q2.Explain the cloud reference model and deployment models.
  3. Q3.Explain approaches to cloud migration and the seven-step model.
  4. Q4.Explain virtualisation, its taxonomy and the Xen, VMware and Hyper-V hypervisors.

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