A framework for modelling and simulating data flows in distributed computing systems

This paper introduces a framework for modelling and simulating the behaviour of distributed computing systems. The framework comprises both means for abstract modelling and an implementation that allows the evaluation of abstract models by means of discrete event simulation. The basic characteristics of distributed computing systems used for physics data processing at CERN are presented, motivating the purpose and need for modelling and simulation. As an example, the central data recording system of a current High-Energy Physics experiment is introduced. The modelling framework provides concepts to structure relevant state information of a system; The most important factor to set up the structure of components encapsulating state information is thereby given by dynamic aspects of the system, i.e. by identified data flows. Traditional approaches to modelling often tend to focus purely on static, architectural system aspects. All abstract concepts are motivated and demonstrated using an example. Results of the simulation are compared to figures measured during real system operation, rating the proposed framework and its underlying modelling approach.