Cost Accounting for Shared IT Infrastructures

Dr. Reinhard Brandl promovierte bei Prof. Dr. Martin Bichler am Lehrstuhl für Internetbasierte Geschäftssysteme der Technischen Universität München. Während seiner Promotion war er als Doktorand am Kompetenzzentrum IT-Architekturen der BMW Group tätig.

During the past few years, determining the "value of IT" has ranked high on the agenda of IT managers and Chief Information O?cers (CIOs). The rather broad and abstract topic has been intensively discussed in the Information Systems literature for many years. It turns into a very tangible problem in the ?eld of IT cost accounting. Nowadays, c- porate information systems are distributed systems. A detailed measurement of resource demands of IT services on a distributed IT-infrastructure and respective accounting and cost allocation turns out to be very expensive and impractical in most cases. The large proportion of indirect costs and the di?culty of ?nding adequate allocation rates are a signi?cant problem in practice, regularly leading to free-rider problems. This problem has largely been ignored in the academic literature so far. Dr. Brandl proposes a method to derive estimators for the resource demand of service requests in a distributed IT infr- tructure. This estimator is based on a set of load tests and respective measurements as they are often performed during the deployment phase of new information systems. Cost allocation keys can now be determined based on the number of service invocations per user or per department and the respective estimators. While these measurements provide a lean method for the determination of usage-based cost allocation keys, it is not obvious that the estimators have su?cient accuracy, in p- ticular concerning di?erent types of services and volatile workloads.

Distributed client/server architectures are the technological backbone of today's data centres. A usage-based allocation of infrastructure costs to business processes or users is often not possible as the necessary resource consumption measurements incur too much overhead.Reinhard Brandl proposes a method to derive estimates for the expected resource consumption of customer-oriented services during standard load tests. This facilitates the determination of usage-based cost allocation keys significantly. He implements the concept in a software tool kit and evaluates it successfully in a set of experiments with multi-tier database applications. In particular, he uses the determined consumption estimates as input parameters for Queuing Network Models which lead to highly accurate performance predictions. Finally, he analyzes how the method can be integrated into existing IT processes at the BMW Group.

IT Infrastructure Cost Allocation.- Cost Allocation based on Resource Profiles.- Experiments: Resource profiles.- Experiments: Analytical Models.- Proof of Concept: BMW Group.- Conclusions.