Team NeCS

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Section: New Results

Modeling and control of web servers

Participants : N. Marchand [ contact person ] , L. Malrait, S. Bouchenak [ SARDES ] .

This work focuses on the design of a server model, the design of admission control laws that allow the server to satisfy different Service Level Objectives, and the implementation of the latter. This work is in collaboration with Sardes team of the INRIA.

The first part of the work consists in designing a continuous time model using a fluid flow approach. Inherent non-linearities of such systems are taken into account. We validate model with different experimental data sets, under different conditions. Results show the relevancy of the model, which is accurate on a wide range of load. Then it is used for control purposes. We build theoretical control laws that ensure a maximum latency on the server or a maximum client rejection rate. We implemented them on a real system which is supposed to emulate an e-business environment. Fig. 8 show the experimental results obtained with a hard workload of one class of requests. A publication has been submitted to the next European Control Conference [49] and a patent is pending.

Figure 8. Evolution of the latency and the client rejection rate (dashed line) for references 8 s for the latency and 20% for the client rejection rate (solid line).
IMG/latenceIMG/rejet

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