Elasticity and scalability are two important characteristics of cloud computing. They describe the way a cloud infrastructure is able to expand and shrink to match the actual dynamic workload, which is described as follows:
- Scalability: This means increasing the capacity of an existing instance (that is, scale up) or adding more instances in parallel to an existing instance (that is, scale out). Scalability is essential in order to achieve elasticity:
- Scale up: Changing the instance type from small to large (that is, changing to more memory or compute) is called scaling up; it is also called vertical scaling. It may require stopping the existing and running instance. Usually, scaling up is done in order to get more compute and memory on the same instance. Scaling up is usually recommended for applications that do not support clustering modes easily...