käyttökatavuus

Käyttökatavuus, often translated as availability or uptime, is a key metric in information technology and engineering that describes the degree to which a system, service, or component is operational and accessible when required. It is typically expressed as a percentage of time a system is functioning correctly. High käyttökatavuus is crucial for businesses and organizations that rely on continuous operation to deliver services, process transactions, or maintain productivity.

Measuring käyttökatavuus involves tracking periods of downtime, which can be caused by various factors including hardware failures, software bugs, network issues, power outages, or planned maintenance. The formula for calculating availability is generally (Total Time - Downtime) / Total Time * 100%. For example, a system with 99.9% availability will experience approximately 8.76 hours of downtime per year, while 99.999% availability (often referred to as "five nines") allows for only about 5.26 minutes of downtime annually.

Achieving high käyttökatavuus often involves implementing redundant systems, robust disaster recovery plans, proactive monitoring, and efficient maintenance procedures. The specific requirements for käyttökatavuus vary significantly depending on the criticality of the service. Mission-critical systems demand extremely high levels of availability, whereas less critical applications might tolerate more frequent or longer periods of unavailability.