Firstly, Uptime can be defined as the time a service/machine has been efficiently rendering service/reliable and stable, without any interruptions or break in service.
Uptime of a service also depends on the availability of that service, because, only when the service is available, it can be used efficiently.
Uptime can be calculated as a difference between availability and downtime of a service.
Uptime = Availability- Downtime
“Availability” = A measure in time where a service is capable of being used.
“Downtime” = When the service is available but gives unreliable service or is not optimal/ has interruptions.
The uptime of a service can also be measured based on customer response and ratings.
StoneFly’s resources/casestudies provides interesting information about service uptime.
Follow the link provided below: