High Availability and Scalability
Understanding scalability in cloud computing is crucial since it allows an application or system to expand its resources to meet critical needs through vertical and horizontal scaling, the latter of which affects high availability.
High Availability
Horizontal scaling, unlike vertical scalability, directly contributes to high availability. As the number of servers increases, so does availability, reducing latency and increasing redundancy. Operating an application or system in multiple Availability Zones is an effective way to achieve high availability, as it mitigates the risk of data center loss due to natural or man-made disasters, aligning with business continuity and disaster recovery plans.
Vertical Scalability
Vertical scalability, also known as scaling up, can meet an increased demand for application or system resources by increasing the size of a cloud instance. For instance, upgrading from a t2.micro instance with 1 vCPU and 1 GiB RAM to a t2.xlarge EC2 instance with 4 vCPU and 16 GiB RAM to accommodate a demand increase is an example of vertical scalability. This type of scalability is commonly used in non-distributed systems like databases.
Horizon Scalability
Horizontal scalability can address availability requirements by scaling in (decreasing the number of instances) or scaling out (increasing the number of instances. A situation with a sudden increased demand for application, system, or compute resources benefits from automatically increasing the number of instances quickly. Conversely, a decrease in server demand will cause a reduction in the number of instances automatically. Scaling in or out is critical to optimizing availability and adapting to the ever-changing needs of cloud resources. Setting up an Auto Scaling Group configured to maintain a specific number of instances at all times, automatically scaling in or out from the set number of instances, makes horizontal scalability possible. To prevent overtaxing any particular instance from incoming requests, configuring a load balancer to optimally route incoming traffic for cloud resources across EC2 instances inside an Auto Scaling Group makes horizontal scalability more efficient and effective.
Scalability vs. Elasticity vs. Agility
Scalability can be achieved by adding more servers to the existing infrastructure (scale out) or upgrading the hardware of the existing servers (scale up) to meet the growing demands of the users. The ultimate goal of scalability is to ensure that the system remains efficient and effective even as the user demand changes.
Elasticity is a critical feature that allows your infrastructure to adapt to changing demand by quickly acquiring or releasing resources once scalability is achieved. With this auto-scaling capability, your cloud-based resources can quickly scale in and out, optimizing costs and efficiency. This feature enables cost savings by allowing for pay-per-use and match-demand models, ensuring that you only pay for what you need and when needed.
Agility allows to quickly and efficiently provide new IT resources to developers, which is a crucial aspect of modern software development. Companies can ensure that new resources are only a click away, reducing the time it takes to make them available from weeks to mere minutes. This results in faster and more efficient software development processes that can keep pace with the demands of today's rapidly changing business landscape.