Mean Time Between Failures (MBTF)

[us3rnotfound]

Having problems understanding the formal definition of MBTF.

It is defined as the sum of (Start of Downtime - Start of Uptime)/Number of Failures. Link: http://en.wikipedia.org/wiki/Mean_time_between_failures.

I thought it should be calculating for the periods of time in which the system is up, not down. Please explain?

Thanks.

EDIT: I think I got it now that I've typed it out and read what I said . The start of downtime will be a greater time value than the start of uptime... Duh.

 

[Murloc]

yeah it's just a mean of the lengths of the intervals in which the thing is up.

 

[MrDudeMan]

MTBF, not MBTF. I was going to write more details, but this link does a good job of explaining it. The wiki article on failure rate also does a good job relating the two terms.