Systems
Reliability
Plain English
How dependable something is.
Definition
Reliability is the ability of a glossarySystemA system is a collection of interconnected components that work together to achieve a specific function or outcome.Open glossary term to consistently perform as expected without failure.
In practice
Measured through glossaryUptimeUptime is the proportion of time a system is operational and reachable, usually expressed as a percentage. It measures availability rather than correctness, so a system can post high uptime while behaving badly.Open glossary term, glossaryError RateError rate measures how often users make mistakes while attempting a task. It is most useful when it separates minor slips users recover from and errors that block progress entirely, because the two need different fixes.Open glossary term, and glossarySystemA system is a collection of interconnected components that work together to achieve a specific function or outcome.Open glossary term stability over time.
In context
It is judged on the bad day, not the average one. A glossarySystemA system is a collection of interconnected components that work together to achieve a specific function or outcome.Open glossary term that is excellent for eleven months and unavailable during the busiest week is remembered as unreliable.
The reality
Reliability is often assumed until failures expose weaknesses.
Compared with
Reliability vs Availability
Availability is whether the glossarySystemA system is a collection of interconnected components that work together to achieve a specific function or outcome.Open glossary term is up. Reliability is whether it does the right thing while it is. A glossaryServiceA service is a component or function that performs a specific task within a system.Open glossary term returning wrong glossaryDataData is raw, uninterpreted information collected and stored so it can be analysed, processed, or used to inform decisions. On its own it carries no meaning; context and interpretation are what make it useful.Open glossary term at full speed is available and unreliable.
FAQ
Common questions
A few practical answers to the questions that usually come up around this term.
What is system reliability?
It is how consistently a glossarySystemA system is a collection of interconnected components that work together to achieve a specific function or outcome.Open glossary term works without failure.
Why is reliability important?
It ensures users can glossaryTrustUser confidence that a product, service, or organisation will do what it promises.Open glossary term the glossarySystemA system is a collection of interconnected components that work together to achieve a specific function or outcome.Open glossary term.
How is reliability measured?
Through glossaryUptimeUptime is the proportion of time a system is operational and reachable, usually expressed as a percentage. It measures availability rather than correctness, so a system can post high uptime while behaving badly.Open glossary term and glossaryError RateError rate measures how often users make mistakes while attempting a task. It is most useful when it separates minor slips users recover from and errors that block progress entirely, because the two need different fixes.Open glossary term.
What causes poor reliability?
Bugs, weak glossaryInfrastructureInfrastructure refers to the underlying systems and resources that support applications and services.Open glossary term, and poor testing.
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