Elasticity versus scalability
Elasticity and scalability are two important characteristics of cloud computing. They describe the way cloud infrastructure is able to expand and shrink to match the actual dynamic workload and are discussed as follows:
- Scalability: This means adding resources either to the existing instance (scale up) or in parallel to an existing instance (scale out). Scalability is essential 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 to get more compute and memory on the same instance. Scaling up is usually suggested for an application that does not support clustering modes easily such as, RDBMS. Usually, scaling up is achieved manually and requires downtime.
- Scale out: Placing one or more new instances parallel to the existing instance is called scale...
