High Availability (HA) describes systems that are dependable enough to operate continuously without failing. They are well-tested and sometimes equipped with redundant components.
“Availability” includes two periods of time: how much time a service is accessible, and how much time the system needs to respond to user requests. High availability refers to those systems that offer a high level of operational performance and quality over a relevant time period.
When it comes to measuring availability, several factors are salient. These include recovery time, and both scheduled and unscheduled maintenance periods.
Typically, availability as a whole is expressed as a percentage of uptime defined by service level agreements (SLAs). A score of 100 percent characterizes a system that never fails.
Netzary delivers High Availability Solutions based on 3 fundamental principles.
Elimination of single points of failure. This means adding or building redundancy into the system so that failure of a component does not mean failure of the entire system.
Reliable crossover. In redundant systems, the crossover point itself tends to become a single point of failure. Reliable systems must provide for reliable crossover.
Detection of failures as they occur. If the two principles above are observed, then a user may never see a failure – but the maintenance activity must.