Why should cloud services offer both elasticity and scalability?
Although elasticity and scalability are two different principles, some IT professionals and other stakeholders tend to think of them as similar, or even, in some cases, as roughly the same thing. This is generally a mistake, as the principles of elasticity and scalability play two different roles in the evolution of IT systems.
The principal of elasticity addresses many of the challenges related to dynamic real-time changes in user demand. The term “rapid elasticity” is often used to describe cloud services that can quickly change capacity for customers. Vendors and customers will also refer to “on-demand services” where companies can quickly order expanded capacity to meet real-time challenges such as peak time management.
With that in mind, elasticity is really made for businesses that have sudden spikes in workload demand. Think of an e-commerce company where flocks of customers tend to flood the system at a given time – for example, where seasonal use varies greatly. Hotels in the summer or retailers near Christmas will want to have systems that can handle greatly increased user demand whenever it tends to occur. By contrast, businesses that have an extremely stable and productive workload management model will not typically need a lot of elasticity in their services, and may not want to pay for it.
The principle of elasticity is also important because it has changed so much of how business works, and revolutionized the concept of business computing over the last decade or so. Handling big changes in real-time demand used to require changes to hardware setups, physical purchasing and other bottlenecks. Now, with on-demand cloud services, companies can experience profound elasticity that helps them to use only the services that they need, at the time that they need them.
Scalability is quite different – it's the building out of the system as general demand increases slowly. Think of a call center that adds employees, or some other system that adds full-time staff to handle gradually increasing customer volume. This growth generally goes one way – outward. It doesn't spike and then recede quickly. Scalability, then, is somewhat of a different principle.
The best cloud services will provide both elasticity and scalability to help businesses manage these two different types of challenges. Business leaders should know how to discuss both of these ideas with vendors, and look over a service-level agreement to make sure that both of these concepts are addressed separately, and not lumped together under some vague description of service provisions.