Performance measurements and modeling of database servers

In this paper we present some experiments on the MySQL database server. The objective of the experiments was to investigate the high load dynamics for varying relation sizes and requests. We show that the dynamics for SELECT (read) requests can be modeled as a modified M/M/1 system, whereas, the dynamics for UPDATE (write) are completely different. Our results can be used for designing control and optimization algorithms for database servers

Application of Control Theory to a Commercial Mobile Service Support System

The Mobile Service Support system (MSS), which Ericsson AB develops, handles the setup of new subscribers and services into a mobile network. Experience from deployed systems show that traffic monitoring and control of the system will be crucial for handling overload situations that may occur at sudden traffic surges. In this paper we identify and explore some important control challenges for this type of systems. Further, we present analysis and experiments showing some advantages of proposed solutions. First, we develop a load-dependent server model for the system, which is validated in testbed experiments. Further, we propose a control design based on the model, and a method for estimation of response times and arrival rates. The main contribution of this paper is that we show how control theory methods and analysis can be used for commercial telecom systems. Parts of our results have been implemented in commercial products, validating the strength of our work

Simulering av styrsystem för tankfartyg

The main purpose of this investigation was to compare, by simulations, the ability of an adaptive regulator and a PID-regulator to keep a ship on desired course with small rudder deflections. Manual steering in confined waters of the simulated ship was also performed. Recordings of delivery tests from real ships were compared to simulations. The non-linear mathematical model of the ship, which was used in the simulations, describes the motion in the horizontal plane. The values of the model parameters are estimated for a 255 000 dwt tanker. Stochastic disturbances to describe the influence of wind and waves were also introduced in the ship model. The adaptive regulator performs a least squares estimation of the parameters in a controller which minimizes the variance of the course error. This regulator gave smaller course errors but larger rudder deviations than a well tuned PID-regulator. The large advantage of the adaptive regulator compared to the PID-regulator is that no manual tuning of parameters for different speeds, loading conditions and weather types is necessary. The manual tuning of the parameters of a PID-regulator has sometimes proved to be difficult to perform on real ships. A conceivable development of the adaptive regulator, which is tested in this report, is to consider the ridder deviations too, when the control is computed

Performance modelling of database servers in a Telecommunication Service Management system

Resource optimization mechanisms, as admission control and traffic management, require accurate performance models that capture the dynamics of the system during high loads. The main objective of this paper is to develop an accurate performance model for database servers in a telecommunication service management system. We investigate the use of a server model with load dependency. Concurrent requests add load to the system and decrease the server capacity. We derive explicit equations for the state probabilities, the average number of jobs in the system and the average response times. Further, we present some heuristics on how to tune the parameters for given measurement data. Also, using testbed experiments, we validate that the model accurately captures the dynamics of a database server with write-heavy workload