Focus on WHAT?!, not only on WHAT?! I have to admit that I have used more meaningful blog post titles in the past. Let me first start by explaining what MTTR and MTBF stands for.
MTBF: Mean time between failures
MTBF (mean time between failures) is the average time between repairable failures of a technology product or system. The metric is used to track both the availability and reliability. The higher the time between failures, the more reliable the system is.
Remark: MTBF is a metric for failures in repairable systems. For failures that require system replacement, typically people use the term MTTF (mean time to failure).
MTTR: Mean time to repair
MTTR (mean time to repair) is the average time it takes to repair a system. It includes both the repair time, testing time and deployment time before the system is back operational.
Why focus on MTTR?
If I talk with system administrators, software architects and CTO’s, a lot of them are mostly focussed on the MTBF metric trying to avoid failures as much as possible. Their primary focus is on the robustness of the system. What can we do to prevent the system from ever going down?
This is a noble effort but if your system runs long enough failure is inevitable. Sooner or later something will break. Also the cost to further increase the MTBF becomes so big that it isn’t worth your money or effort.
If you only focused on MTBF, you are into trouble. How much time will it take to get the system back up and running? Especially when your system has a high MTBF, repairs are rare and therefore typically not well practiced.
Therefore not only focus on MTBF but also on MTTR. Not only create a disaster recovery plan but also test it. Train your IT staff so that they are ready when an outage occurs.
Remark: Next to robustness and reparability, you can bring this to the next level by also focusing on resiliency but that is something for another post.