Which factor is a measurement of system reliability?

A.
Recovery point objective

B.
Mean time between failures

C.
Mean time to repair

D.
Recovery time objective

Explanation:
Measuring Information Availability
Information availability relies on the availability of both physical and virtual components of a data
center. Failure of these components might disrupt information availability. A failure is the
termination of a component’s ability to perform a required function. The component’s ability can be
restored by performing an external corrective actions, such as a manual reboot, a repair, or
replacement of the failed component(s). Proactive risk analysis, performed as part of the BC
planning process, considers the component failure rate and average repair time, which are
measured by MTBF and MTTR:

Mean Time Between Failure (MTBF): It is the average time available for a system or component to
perform its normal operations between failures. It is the measure of system or component
reliability and is usually expressed in hours.
Mean Time To Repair (MTTR): It is the average time required to repair a failed component.
MTTR includes the total time required to do the following activities: detect the fault, mobilize the
maintenance team, diagnose the fault, obtain the spare parts, repair, test, and restore the data.
MTTR is calculated as: Total downtime/Number of failures IA can be expressed in terms of system
uptime and downtime and measured as the amount or percentage of system uptime:
IA = system uptime / (system uptime + system downtime)
Where system uptime is the period of time during which the system is in an accessible state; when
it is not accessible, it is termed as system downtime.
In terms of MTBF and MTTR, IA could also be expressed as: IA = MTBF / (MTBF + MTTR)