CLOUD COMPUTING: WHAT IT IS

(Femi Adewumi, 2017)

The US National Institute of Science and Technology, NIST (2011) defines “cloud computing as

"... a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources (e.g. networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction" (NIST, 2011)

Cloud computing is a departure from the traditional way IT services are delivered, paid for and managed. The model delivers IT infrastructure, applications, and other components of IT from data centers owned by service providers helping the consumers avoid capital IT investments. Access to these IT elements are delivered as services which the consumers pay for as they use them. It transforms IT services into a utility like electrical power or water supply, being ubiquitous and able to scale easily with demand. North Bridge’s (2014) survey revealed the cloud based application demand quintupled between 2011 and 2014

The basic attribute of a cloud service is that it is delivered remotely over a network, allowing users to provision computing resources by themselves and giving them the ability to dynamically increase or decrease the capacity subscribed to as required along with metering capabilities to measure and bill them for usage (Yang & Tate, 2012).

Cloud services come in three basic models, public, private and hybrid clouds. Public clouds are delivered out of the service providers' data centers and are available to the public (e.g. IBM's Softlayer, Amazon's AWS and Microsoft Azure) while private clouds are dedicated to the consumers. The hybrid cloud combines both, allowing the consumers to have the dedicated facilities while integrating with the public cloud to dynamically provide access to computing resources as needed (Mujinga and Chipangura 2011b, Yang and Tate 2012) - Fig1.1.

Fig1.1: Cloud subtypes and adoption framework (Source: IBM, www-935.ibm.com/services/us/cio/itxpo/4_defining-a-framework-for-cloud-adoptionciw03067usen.pdf)

The services are delivered using different models each presenting different elements of the IT strata "as a service" e.g. Infrastructure as a service (IaaS) where complete servers or components of hardware (e.g. storage) and data center resources are offered to the consumers, or Platform as a service (PaaS) where complete server builds and middleware (like databases and application web services) are provided to the customers and lastly, Software as a Service (SaaS) where access to applications e.g. SAP or Microsoft's Office 365 are provided as a service completely obscuring the supporting data center or processing resources from the customer (Owens, 2010), Fig1.2.

Fig1.2: Cloud service types (Source: IBM, www-935.ibm.com/services/us/cio/itxpo/4_defining-a-framework-for-cloudadoptionciw03067usen.pdf)