Having better service capacity with high availability and low latency is mission critical for ALMOST all businesses.
Availability MEANS the ability of the application user to access the system, If a user cannot access the application, it is assumed unavailable. High Availability means the application will be available, without interruption.
Achieving high availability for a application is not always a easy task. Using redundant server nodes with clustering is a common way to achieve HIGHERLEVEL of availability in web applications.
Availability is commonly expressed as a percentage of UPTIME in a given year.