Deriving a Good Trade-off Between System Availability and Time Redundancy
Nils Müllner, Abhishek Dhama, Oliver Theel · 2009
What to do if at a given time a service dearly required is unavailable? Is it a good strategy to simply invoke the service again (and again)? How many times should one retry in such a situation in order to get a the service delivered with a reasonably high probability but without "losing too much time?" In this paper, we explore the relation between time redundancy that a system can utilize to cope with faults and the increase of system availability. We propose a generalization of instantaneous availability called instantaneous window availability to systematize our approach. We then present two methods for deriving trade-off solutions in terms of average instantaneous window availability, namely Markov model analysis and discrete-time simulation. We apply these methods to two instances of a self-stabilizing system and discuss the outcome.