# High availability
High availability refers to a system or component that is durable and operates continuously without failure for a higher than normal period. Availability is usually expressed as a percentage of uptime in a given year. High Availability relative to “100% operational” or “never failing.”
# Fault tolerant
Fault tolerance is the capability of a component or a computer system to respond to an unexpected software or hardware failure to deliver uninterrupted service and to continue operating properly in the event of the failure of its components.
Scalability is the capability of a system, network, or process to handle an increasing amount of work (load), or its potential to be enlarged to accommodate that growth in load.
Elasticity is the ability to adapt workload changes by provisioning and de-provisioning resources in an autonomic manner, such that at each point in time the available resources match the current demand as closely as possible.