Availability: The percentage of time your system is operational. Measured in "nines."
- % = days of downtime per year
- % = hours of downtime per year
- % = minutes of downtime per year
- % = minutes of downtime per year
Reliability: The system produces correct results. A system can be available but unreliable (responds, but with wrong data).
Most systems target % to % availability. % is expensive and difficult to achieve.