Load balancing in distributed Web server systems with partial document replication

摘要

How documents of a Web site are replicated and where they are placed among the server nodes have an important bearing on balance of load in a geographically distributed Web server (DWS) system. The traffic generated due to movements of documents at runtime could also affect the performance of the DWS system. In this paper, we prove that minimizing such traffic is NP-hard. We propose a new document distribution scheme that periodically performs partial replication of a site's documents at selected server locations to maintain load balancing. Several approximation algorithms are used in it to minimize traffic generated. The simulation results show that this scheme can achieve better load balancing than a dynamic scheme, while the internal traffic it causes has a negligible effect on the system's performance.