Cloud Model Comparison

According to the layers from top to bottom, at top most we have Software as a Service, follow by Platform as a Service and bottom most Infrastructure as a Service.

First we discuss SaaS. SaaS is essentially providing software traditionally need to be purchase by licenses into a pay as you used model.

Software as a Service(SaaS)-  Cloud Applications

Complexity : Low
Flexibility : Minimal Control, determine by apps provider, minimal customization
Consumers: End Users
Type of services: Webmails, MessageLabs, Virus Scanners, online office suite-zoho, CloudFront etc
Pricing: Price based on per used basis.
Benefits: 

• Save Time & Cost, 
• Budget focus of competitive advantage instead of infrasturture,
• Utility model of pay as you used, without worrying of licenses or version upgrades
• Faster to start use, no need to install.
• Flexible & Scalable and 
• Multi-tenant efficiency.

Examples: GoogleApps, Salesforce.com, Cybershift, Zoho, TurboTax Online, Microsoft Online Services, MailTrust.



PaaS provide a platform for business to quickly churn out applications without worrying about setting up servers and development tool licenses. Sometime SaaS can also ride on top of PaaS

Platform as a Service(SaaS)- Cloud Platforms

Complexity : Middle

Flexibility : Medium Control

Consumers: Developers, Programmers,

Type of services: development system, debugging and testings, deployment

Pricing: Price based on per used basis.

Benefits:

• Multi-location development sites working together possible 
• Multi interaction development
• Cost reductions derived from using built-in infrastructure services
• Cost reductions derived from using highlevel programming abstractions
• Opensource and standardization possible
• Multi-tenant efficiency.

Examples: Amazon Web Services, GoogleAppEngine, Force.com, WindowsAzure, engineyard(based on rails on cloud), WolfFramework

(below is the comparison chart extracted courtesy of zdnet.com article comparing "Amazon's and Google's Platform-as-a-Service (PaaS) Offerings")

IaaS abstract the computer infrastructure of a system. It can sometime be also refers as Everything as a Service model as it can also include PaaS and SaaS in it.

Infrastructure as a Service(SaaS)-  Cloud Infrastructure

Complexity :High 

Flexibility : Full Control

Consumers: Systems Administrators

Type of services: development system, debugging and testings, deployment

Pricing: Price by utilisation, size, performance.

Benefits: 

• Resources delivered as a service
  
• Dynamic scaling of infrastructure(Elasticity) 
• Lower CapEx as infrastructure is used as service
• Enterprise graded infastructure can be used by mid or small size company to benefit due to aggregated sharing
• Multi-tenant efficiency.

Examples: Amazon EC2, Nebula NASA, Flexiscale

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Annex A

comparison chart extracted courtesy of zdnet.com article comparing "Amazon's and Google's Platform-as-a-Service (PaaS) Offerings"