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Another memory trick to calculate the allowed downtime duration for an "-nines" availability percentage is to use the formula seconds per day. For example, 90% ("one nine") yields the exponent 4 − 1 = 3 {\displaystyle 4-1=3} , and therefore the allowed downtime is 8.64 × 10 3 {\displaystyle 8.64\times 10^{3}} seconds per day.
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.
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
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.
First order LTI systems are characterized by the differential equation + = where τ represents the exponential decay constant and V is a function of time t = (). The right-hand side is the forcing function f(t) describing an external driving function of time, which can be regarded as the system input, to which V(t) is the response, or system output.
For an approximately normal data set, the values within one standard deviation of the mean account for about 68% of the set; while within two standard deviations account for about 95%; and within three standard deviations account for about 99.7%.
The term "second" comes from "the second minute division of an hour", as it is 1 ⁄ 60 of a minute, or 1 ⁄ 60 of 1 ⁄ 60 of an hour. While usually sub-second units are represented with SI prefixes on the second (e.g. milliseconds ), this system can be extrapolated further, such that a "Third" would mean 1 ⁄ 60 of a second (16.7 ...
The basic problem considers all trials to be of one "type". The birthday problem has been generalized to consider an arbitrary number of types. [20] In the simplest extension there are two types of people, say m men and n women, and the problem becomes characterizing the probability of a shared birthday between at least one man and one woman ...