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Unavailability refers to the state or condition where the system or specific components within the system are unavailable. It is the complement of availability and represents the proportion of time a system is not operational.
The calculator uses the formula:
Where:
Explanation: This formula calculates the proportion of time a system is unavailable based on its availability percentage.
Details: Calculating unavailability is crucial for system reliability analysis, maintenance planning, and service level agreement (SLA) compliance. It helps identify system downtime and improve overall system performance.
Tips: Enter availability value between 0 and 1 (e.g., 0.95 for 95% availability). The calculator will compute the corresponding unavailability value.
Q1: What is the relationship between availability and unavailability?
A: Availability and unavailability are complementary values that sum to 1. If a system has 95% availability, it has 5% unavailability.
Q2: How is unavailability typically expressed?
A: Unavailability can be expressed as a decimal (0.05), percentage (5%), or downtime per year (approximately 18.25 days for 95% availability).
Q3: What factors contribute to system unavailability?
A: Unavailability can result from planned maintenance, hardware failures, software issues, network outages, power failures, and other system disruptions.
Q4: How can unavailability be reduced?
A: Unavailability can be reduced through redundancy, failover systems, preventive maintenance, improved monitoring, and faster recovery procedures.
Q5: What is considered acceptable unavailability for critical systems?
A: Acceptable unavailability varies by industry. Critical systems often aim for 99.999% availability (five nines), which corresponds to about 5 minutes of unavailability per year.