Scalability and high availability are two critical concepts in cloud computing, emphasising the ability of the cloud systems to handle various workload, mean while ensuring uninterrupted cloud service delivery. They demonstrate the resilience and effectiveness of a cloud architectures.
Scalability
Scalability is the property of a system to handle great amount of workload, or to be easily expanded, in response to increased demand for network, processing, database access, or file system resources. There are two kinds of scalability: vertical scalability and horizontal scalability (elasticity).
Vertical scalability
A system scale vertically, when it is expanded by increasing the capacity of a single resource, such upgrading to a more powerful sever with more CPU and memory. (In AWS you can upgrade your t2.micro EC2 instance to a t2.large instance for greater computing power and storage size)
Horizontal scalability (elasticity)
A system scale horizontally is by adding more instances or resources to distribute the load across multiple machines (distributed system). Elasticity is the ability of dynamically and automatically scale resources up or down on demand, preventing over-provisioning or under-provisioning. (Amazon provides many horizontal scalability tools such as Amazon EC2, ELB and ASG)
High availability
High availability refers to the design and implementation of a system to ensure it remains operational and accessible for maximum amount of time, minimising the system downtime and providing continuous service even under unforeseen events such as data centre power outage. (In Amazon, the high availability is achieved by running instances for the same application across multiple Availability Zone, and using the ELB and ASG)
Back to parent node: Cloud Computing
Cloud_computingAWSAWS_CLF-C02ScalabilityHigh_availabilityElasticityEC2ELBASG
Reference - Udemy Ultimate AWS Certified Cloud Practitioner CLF-C02