Performance Analysis of a Controlled Database Unit Subject to Control Delays and Decision Errors

This paper is an extension of the work performed by Wu, Metzler, and Linderman on a controlled database unit. The system configuration has been changed from the earlier work to help further enhance the database performance. When a server fails, state variable feedback is used to trigger the process of server restoration. In this paper, control delays and decision errors due to the time required and the uncertainty present in estimating the state are captured simultaneously within a single model of the system, whereas they were studied separately in two different models in the earlier work. The performance of the database unit is evaluated in terms of its mean time to failure, steady state availability, expected response time, and service overhead. These performance measures are examined with respect to the probability of correct decision to restore a server upon its failure, the length of control action delay, and the rate of server restoration.