Availability Testing

[HanneSThEGreaT]

Hello! :wave:

In my book I have the following:
Definition of Availability
Availability is a measure of how often the application is available to handle service requests as compared to the planned run time. Availability also takes into account repair time because an application that is being repaired is not available for use

MTBF = Mean Time Between Failure
MTTR = Mean Time To Recovery

Ok, I understand it.
The formula used for calculating availability is:
Availability = (MTBF / (MTBF + MTTR)) * 100

I understand that as well.

NOW the book gives me the following example:
The typical availability requirement for the CompanyName application is that the site is available for 24 hours a day, 7 days a week. If you assume 1000 continuous hours as a checkpoint, two 1-hour failures during this time period results in availability of:

((1000 / 2) / ((1000 / 2) + 1)) * 100 = (500 / 501) * 100 = .998 * 100 = 99.8%

:confused: :eek: :ehh:

Can someone please explain the above formula to me, because me and maths aren't good friends ¿

Thanx

[klintan]

MTTR=1 (1 hour to repair)
MTBF=1000/2=500 (2 failures during 1000 hours)

Avaliability=(MTBF/(MTBF+MTTR))*100=(500/(500+1))*100=99.8