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A system that has been up for 365 days in a non-leap year might have been eclipsed by a network failure that lasted for 9 hours during a peak usage period; the user community will see the system as unavailable, whereas the system administrator will claim 100% uptime. However, given the true definition of availability, the system will be ...
In this context, a "one nine" (90%) uptime indicates a system that is available 90% of the time or, as is more commonly described, unavailable 10% of the time – about 72 hours per month. [8] A "five nines" (99.999%) uptime describes a system that is unavailable for at most 26 seconds per month.
Five nines, commonly taken to mean "99.999%", may refer to: High availability of services, when a service is available for 99.999% of the time, or around 5 minutes of downtime per year; Nine (purity), a 99.999% pure substance; German 15 cm (5.9 in) artillery shells used in World War I
Uptime is a measure of system reliability, expressed as the period of time a machine, typically a computer, has been continuously working and available. Uptime is the opposite of downtime . Htop adds an exclamation mark when uptime is longer than 100 days.
Availability is the probability that an item will be in an operable and committable state at the start of a mission when the mission is called for at a random time, and is generally defined as uptime divided by total time (uptime plus downtime).
Mean Time To Discover is statistical when PMS is the dominant maintenance philosophy. For example, if a fault is discovered during PMS diagnostic procedure that is run every 10 days, the average fault duration will be 5 days. This creates a dependency between availability performance and labor costs. There is no such dependency associated with CBM.
That's four nines or five nines of availability and uptime for their mission-critical line-of-business applications. And 9% of the respondents, so that's almost one out of 10 companies, say that they need greater than five nines of uptime. So what that means is, no downtime.
Availability is usually expressed as a percentage of uptime in a given year: Availability Downtime per year 99.9% 8.76 hours 99.99% 1 hour 99.999% 5 minutes