Cloud Computing Models -SaaS, PaaS, IaaS

By | November 28, 2016

Cloud Computing Models -SaaS, PaaS, IaaS

Software as a Service (SaaS)

SaaS is a cloud model in which users access software, programs, and data in the cloud. SaaS services are commonly accessed with a web browser. SaaS allows organizations an affordable way to access a wide variety of applications while eliminating the requirement for in-house hosted applications, hosting hardware, application support and administration, and data storage.  SaaS applications are multi-tenant solutions meaning two or more organizations may share the same resources to include database resources.

Advantages of SaaS include the following:

  • Reduce or eliminate the requirement for an on-site data centers
  • Eliminate the requirement for application administration
  • Pay on a per user basis for on demand software use
  • Application, storage, and processing scaling to accommodate higher demand
  • Better disaster recovery and business continuity
  • Organizations can keep copies of critical data locally and keep copies on the cloud.

Disadvantages of SaaS include the following:

  • Security. Sensitive organization data and its security is being entrusted to a third-party
  • Outages. Service Level Agreements (SLA) need to be clear and detailed.
  • Compliance. SaaS applications must be in compliance with specific business and security laws if required.
  • Performance. Not all applications are well suited for running in a browser.
  • Availability. SLA’s can provide guaranteed levels of performance and availability, but SLA’s do not apply to communications and internet providers. Access to a SaaS application relies on reliable network connectivity.
  • Integration with existing and legacy applications is not always easy and depends much on API’s and other interfaces supplied by the cloud vendor.


Platform as a Service (PaaS)

PaaS is a cloud model that provides software and hardware resources that developers can use to build and deploy their own applications. PaaS allows developers to eliminate the need to purchase and maintain hardware, administer Operating Systems (OS), and databases. This leaves more time for the actual development and deployment of applications.. Developers can choose Windows-based and Linux-based solutions.

Advantages of PaaS include the following:

  • Lower cost of ownership since organizations do not need to buy and maintain server, power, and storage hardware.
  • Lower administrative overhead since most maintenance and administration of the underlying system is handled by the cloud vendor.
  • System software and patches are kept current by the cloud vendor.
  • Better business and IT alignment since an organizations IT staff can focus on solutions rather than server related maintenance and upkeep.
  • Scalable. Cloud solutions can be configured to scale up or down automatically based on demand. This allows the organization to only pay for resources they are actually using.

Disadvantages of PaaS include the following:

  • Data security. Some organizations have concerns and are reluctant to move storage off-site where they cannot control security of their data.
  • Integrating new cloud solutions with legacy software. Integration between different application types may be difficult or impossible.
  • Breach of service agreement by the PaaS provider. If the provider fails to meet contracted service levels of performance, security, and availability, it may be difficult to move applications to another provider.


Infrastructure as a Service (IaaS)

IaaS is a cloud model where the cloud vendor provides computing hardware and resources for customers to install and manage their own systems. In this model the provider handles server hardware but the customer installs OS’s of their choosing and manage their environment through a management application often accessible through a web browser.  This model allows organizations to deploy their own data centers without the need to buy, host, and maintain the hardware themselves, and allows them to control the management and security of their system. As with SaaS and PaaS, IaaS allows an organization pay only for the resources that it actually uses. IaaS typically provides resources as either a physical server dedicated to a customer, a dedicated virtual server, or a shared virtual server.

Advantages of IaaS include the following:

  • Elimination of data center hardware and maintenance staff.
  • Scalability.
  • Lower hardware costs.
  • Pay as you go billing model that allows an organization to pay for only the resources they use.
  • Reduced IT staff. Easily setup test environments using virtualization.
  • Retain full system administration and management.

Disadvantages of IaaS include the following:

  • IaaS is usually the most expensive cloud model since customers are using clearly tangible resources that can be itemized into very low increments of measure. Example; bits of storage and processor cycles.
  • Customers using this model are responsible for configuring their own load balancing, fail-over, and are responsible for doing their own backups.
  • Unlike PaaS and SaaS, customers are responsible for Virtual Machine (VM) management.
  • Even though customers control their own software and configuration, they often do not have control over aspects such as where their data will be geographically located.




AIA, SaaS, PaaS, IaaS. (2015, September 10). Advantages and Disadvantages of SaaS,PaaS and IaaS. Retrieved July 5, 2016, from

McClellan, C. (2013, March 04). SaaS: Pros, cons and leading vendors. Retrieved July 5, 2016,    from

The Open Group- Why Cloud? (n.d.). Cloud Computing for Business-Why Cloud? Retrieved July 7, 2016, from



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