IS PREVENTION ALWAYS BETTER? A CASE OF IT SERVICE MANAGEMENT

Information Technology Infrastructure Library (ITIL), a framework for IT Service Management (ITSM), emphasizes the need for an ongoing preventive activity woven into the fabric of enterprise IT of organizations as opposed to a reacting to a specific situation. However, with the increasing focus on cost reduction, it is essential to revisit the trade-off between costs and other primary ITSM objectives such as service availability and quality. With this basic premise, we compare the cost of conducting IT service operations with varying levels of prevention. We modelled the IT service operation processes based on queuing and software reliability theories while assessing the impact of exogenous variables such as initial application maturity, drop rates & monitoring cost. We illustrated that optimum lies between the extremes of complete prevention and reaction. Also, we were able to observe the pronounced impact of staffing stickiness on the results

On the Effectiveness of Buffer in Deterministic Services

We study the utility of buffer at switches in increasing the achievable utilization of a network providing deterministic guarantee. To determine the increase in utilization, we classify packet scheduling algorithms into two classes. Only one of these classes can utilize additional buffers to increase the achievable utilization. We experimentally determine the difference in achievable utilization of these classes. Our experiments demonstrate that contrary to intuition, in most cases, additional buffers do not lead to higher achievable utilization of a network. 1 Introduction Integrated services networks support a diverse set of applications (e.g., data, audio, interactive video, stored video applications). The traffic characteristics as well as Quality of Service (QoS) requirements of these diverse applications vary significantly. To meet the QoS of requirements of the applications, a network has to manage two resources: link bandwidth and packet buffers. While several packet schedulin..

Analyzing the performance of asynchronous disk arrays for multimedia retrieval

Due to the periodic nature of media playback, a multimedia server can service multipleclients simultaneouslyby proceeding in rounds, retrieving a fixed number of media units (e.g., video frames) for each client during each round. In this paper, we analyze the performance of a conservative and an aggressive policy for retrieving media units from an asynchronous disk array. In the conservative servicing policy, a server completely retrieves all the required media units during a round prior to initiating the next round. A server employing the aggressive servicing policy, on the other hand, requires the disks to synchronize only over a finite sequence of rounds. We have carried out extensive simulations to measure the effectiveness of the conservative and the aggressive servicing policies on the utilization of asynchronous disk arrays. We present and analyze our simulation results

Efficient Striping Techniques for Multimedia File Servers

The performance of striped disk arrays is governed by two parameters: the stripe unit size and the degree of striping. In this paper, we describe techniques for determining the stripe unit size and degree of striping for disk arrays storing variable bit rate continuous media data. We present an analytical model that uses the server configuration and the workload characteristics to predict the load on the most heavily loaded disk in redundant and non-redundant arrays. We then use the model to determine the optimal stripe unit size for different workloads. We also use the model to study the effect of various system parameters on the optimal stripe unit size. To determine the degree of striping, we first demonstrate that striping a continuous media stream across all disks in the array causes the number of clients supported to increase sub-linearly with increase in the number of disks. To maximize the number of clients supported in large arrays, we propose a technique that partitions a dis..