Database Reference
In-Depth Information
Utility Computing
Utility computing represents the business model of packaging resources as a
metered services similar to those provided by traditional public utility companies.
In particular, it allows provisioning resources on demand and charging customers
based on usage rather than a flat rate. The main benefit of utility computing is better
economics. Cloud computing can be perceived as a realization of utility computing.
With on-demand resource provisioning and utility-based pricing, customers are able
to receive more resources to handle unanticipated peaks and only pay for resources
they needed; meanwhile, service providers can maximize resource utilization and
minimize their operating costs.
2.3
Cloud Service Models
The categorization of three cloud service models defined in the guideline are also
widely accepted nowadays. The three service models are namely
Infrastructure as
a Service
(IaaS),
Platform as a Service
(PaaS), and
Software as a Service
(SaaS).
As shown in Fig.
2.3
, the three service models form a stack structure of cloud
computing, with Software as a Service on the top, Platform as a Service in the
middle, and Infrastructure as a Service at the bottom, respectively. While the
inverted triangle shows the possible proportion of providers of each model, it is
worth mentioning that definitions of three service models from the guideline paid
more attentions to the customers' view. In contrast, Vaquero et al. [
225
] defined
Software as a Service (SaaS)
Salesforce.com
Google Apps (Gmail, Docs, …)
Zoho
Platform as a Service (PaaS)
Google App Engine
Microsoft Azure
Heroku
Infrastructure as a Service
(IaaS)
Amazon EC2
GoGrid
Fig. 2.3
The service models of cloud computing
