The effect of system workload on error latency: an experimental study

In this paper, a methodology for determining and characterizing error latency is developed. The method is based on real workload data, gathered by an experiment instrumented on a VAX 11/780 during the normal workload cycle of the installation. This is the first attempt at jointly studying error latency and workload variations in a full production system. Distributions of error latency were generated by simulating the occurrence of faults under varying workload conditions. A family of error latency distributions so generated illustrate that error latency is not so much a function of when in time a fault occurred but rather a function of the workload that followed the failure. The study finds that the mean error latency varies by a 1 to 8 (hours) ratio between high and low workloads. The method is general and can be applied to any system.