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Unit 5: Cloud Computing for the Community

maintaining it. The client typically pays on a per-use basis. IaaS is a standardized, highly Notes
automated offering, where compute resources, complemented by storage and networking
capabilities are owned and hosted by a service provider and offered to customers on-demand.
Customers are able to self-provision this infrastructure, using a Web-based graphical user
interface that serves as an IT operations management console for the overall environment.
API access to the infrastructure may also be offered as an option.

Platform-as-a-Service (PaaS)

Platform as a Service is a way to rent hardware, operating systems, storage and network capacity
over the Internet. The service delivery model allows the customer to rent virtualized servers
and associated services for running existing applications or developing and testing new ones.
Platform as a Service is an outgrowth of Software as a Service, a software distribution model in
which hosted software applications are made available to customers over the Internet. PaaS has
several advantages for developers. With PaaS, operating system features can be changed and
upgraded frequently. Geographically distributed development teams can work together on
software development projects. Services can be obtained from diverse sources that cross
international boundaries. Initial and on-going costs can be reduced by the use of infrastructure
services from a single vendor rather than maintaining multiple hardware facilities that often
perform duplicate functions or suffer from incompatibility problems. Overall expenses can also
be minimized by unification of programming development efforts.

On the downside, PaaS involves some risk of “lock-in” if offerings require proprietary service
interfaces or development languages. Another potential pitfall is that the flexibility of offerings
may not meet the needs of some users whose requirements rapidly evolve.

Software-as-a-Service (SaaS)

Software as a Service is a software distribution model in which applications are hosted by a
vendor or service provider and made available to customers over a network, typically the
Internet.’ SaaS is becoming an increasingly prevalent delivery model as underlying technologies
that support Web services and Service-oriented Architecture (SOA) mature and new
developmental approaches, such as Ajax, become popular. Meanwhile, broadband service has
become increasingly available to support user access from more areas around the world.
Software as a Service delivers business processes and applications, such as CRM, collaboration,
and email, as standardized capabilities for a usage-based cost at an agreed, business-relevant
service level.
SaaS is closely related to the ASP (application service provider) and on demand computing
software delivery models. IDC identifies two slightly different delivery models for SaaS. The
hosted application management (hosted AM) model is similar to ASP: a provider hosts
commercially available software for customers and delivers it over the Web. In the software on
demand model, the provider gives customers network-based access to a single copy of an
application created specifically for SaaS distribution.

Benefits of the SaaS model includes easier administration, automatic updates and patch
management, compatibility wherein all users will have the same version of software,
easier collaboration for the same reason and global accessibility. SaaS provides significant
efficiencies in cost and delivery in exchange for minimal customization and represents a shift of
operational risks from the consumer to the provider. All infrastructure and IT operational
functions are abstracted away from the consumer.

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