Volume 3595 of the series Lecture Notes in Computer Science pp 632643
Server Allocation Algorithms for Tiered Systems
 Kamalika ChaudhuriAffiliated withComputer Science Division, University of California
 , Anshul KothariAffiliated withComputer Science Depart, University of California
 , Rudi PendavinghAffiliated withDepart. of Math. and CS., TU Eindhoven
 , Ram SwaminathanAffiliated withHP Labs
 , Robert TarjanAffiliated withHP Labs
 , Yunhong ZhouAffiliated withHP Labs
Abstract
Many webbased systems have a tiered application architecture, in which a request needs to transverse all the tiers before finishing its processing. One of the most important QoS metrics for these applications is the expected response time for the user. Since the expected response time in any tier depends upon the number of servers allocated to this tier, and a request’s total response time is the sum of the response times at all the tiers, many different configurations (number of servers allocated to each tier) can satisfy the expected response time requirement. Naturally, one would like to find the configuration to minimize the total system cost while satisfying the total response time requirement. This is modeled as a nonlinear optimization problem using an openqueuing network model of response time, which we call the server allocation problem for tiered systems (SAPTS).
In this paper we study the computational complexity of SAPTS and design efficient algorithms to solve it. For a variable number of tiers, we show that the decision problem of SAPTS is NPcomplete. Then we design a simple twoapproximation algorithm and a fully polynomial time approximation scheme (FPTAS). If the number of tiers is a constant, we show that SAPTS is polynomialtime solvable. Furthermore, we design a fast polynomialtime exact algorithm to solve for the important twotier case. Most of our results extend to the general case where each tier has an arbitrary response time function.
 Title
 Server Allocation Algorithms for Tiered Systems
 Book Title
 Computing and Combinatorics
 Book Subtitle
 11th Annual International Conference, COCOON 2005 Kunming, China, August 16–19, 2005 Proceedings
 Pages
 pp 632643
 Copyright
 2005
 DOI
 10.1007/11533719_64
 Print ISBN
 9783540280613
 Online ISBN
 9783540318064
 Series Title
 Lecture Notes in Computer Science
 Series Volume
 3595
 Series ISSN
 03029743
 Publisher
 Springer Berlin Heidelberg
 Copyright Holder
 SpringerVerlag Berlin Heidelberg
 Additional Links
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 Editors

 Lusheng Wang ^{(1)}
 Editor Affiliations

 1. Department of Computer Science, City University of Hong Kong
 Authors

 Kamalika Chaudhuri ^{(2)}
 Anshul Kothari ^{(3)}
 Rudi Pendavingh ^{(4)}
 Ram Swaminathan ^{(5)}
 Robert Tarjan ^{(5)}
 Yunhong Zhou ^{(5)}
 Author Affiliations

 2. Computer Science Division, University of California, Berkeley, CA, 94720, USA
 3. Computer Science Depart, University of California, Santa Barbara, CA, 93106, USA
 4. Depart. of Math. and CS., TU Eindhoven, Eindhoven, The Netherlands
 5. HP Labs, 1501 Page Mill Rd, Palo Alto, CA, 94304, USA
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