nA
simple measure of reliability is mean-time-between-failure (MTBF), where
n MTBF = MTTF + MTTR
nThe
acronyms MTTF and MTTR are mean-time-to-failure and mean-time-to-repair,
respectively.
nSoftware availability is the probability that
a program is operating according to requirements at a
given point in time and is defined as
n Availability =
[MTTF/(MTTF + MTTR)] x 100%