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Figure 3.1: The consumers of SaaS, PaaS, and IaaS
Inthischapter,wewilldiscusstheseservicesintermsofbeingprovidedbyathird-party
vendor since that is the general case.
A platform may be described along three axes:
•
Level of service abstraction:
IaaS, PaaS, SaaS
•
Type of machine:
Physical, virtual, or process container
•
Level of resource sharing:
Shared or private
3.1 Level of Service Abstraction
Abstractionis,essentially,howfarusersarekeptfromthedetailsoftherawmachineitself.
That is,areyouofferedarawmachine (lowabstraction) orareservices providedasahigh-
levelAPIthatencapsulateswhatyouneeddoneratherthanhowtodoit(highabstraction)?
The closer you are to the raw machine, the more control you have. The higher the level of
abstraction, the less you have to concern yourself with technical details of building infra-
structure and the more you can focus on the application.
3.1.1 Infrastructure as a Service
IaaS provides bare machines, networked and ready for you to install the operating system
andyourownsoftware.Theserviceproviderprovidestheinfrastructuresothatthecustom-
er can focus on the application itself.
The machines provided by the vendor are usually virtual machines but may be physical
machines. The provider takes care of the infrastructure: the machines themselves, power,
cooling, and networking, providing internet access, and all datacenter operations.
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