Which metric best indicates the time a telemetry system remains operational before a failure occurs?

• A. Availability
• B. MTTR
• C. MTBF
• D. SLA adherence

Answer: (C)

Reliability and uptime duration between failures is what’s being measured here. MTBF, or mean time between failures, captures the expected operational period before a failure occurs. It’s calculated by taking the total time the telemetry system runs and dividing by the number of failures, so it directly reflects how long the system stays up on average before something goes wrong. This is exactly the time-between-failures metric, which is what the question asks for.

Consider how the other metrics differ: Availability looks at the share of time the system is up over a given period, mixing both uptime and downtime into a single ratio rather than focusing on the length of each up-time interval. MTTR measures how long it takes to repair a failure, i.e., the downtime after a fault, not how long the system runs before a fault. SLA adherence is about meeting contractual performance targets, like uptime or response time, rather than describing the typical time between failures.