Uptime is a measure of system reliability expressed as the percentage of time a service is available and functioning correctly. It is the inverse of downtime: a service with 99.9% uptime experiences 0.1% downtime, which translates to about 8.77 hours per year.
Uptime is the most commonly used metric in SLAs and is often expressed using the "nines" notation: 99% (two nines), 99.9% (three nines), 99.99% (four nines), and 99.999% (five nines). Each additional nine dramatically reduces the allowable downtime.
Achieving high uptime requires a combination of redundant infrastructure, proactive monitoring, automated failover, well-rehearsed incident response processes, and continuous improvement through postmortems. Hyperping monitors your services from multiple global locations to detect downtime within seconds.
