Approximate Algorithms for Document Placement in Distributed Web Servers

  • Authors:
  • Savio S. H. Tse

  • Affiliations:
  • -

  • Venue:
  • IEEE Transactions on Parallel and Distributed Systems
  • Year:
  • 2005

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Abstract

We study approximate algorithms for placing a set of documents into M distributed Web servers in this paper. We define the load of a server to be the summation of loads induced by all documents stored. The size of a server is defined in a similar manner. We propose five algorithms. Algorithm 1 balances the loads and sizes of the servers by limiting the loads to k_l and the sizes to k_s times their optimal values, where {\frac{1}{k_l-1}}+{\frac{1}{k_s-1}}\leq 1. This result improves the bounds on load and size of servers in. Algorithm 2 further reduces the load bound on each server by using partial document replication, and Algorithm 3 by sorting. Algorithm 4 employs both partial replication and sorting. Last, without using sorting and replication, we give Algorithm 5 for the dynamic placement at the cost of a factor O(\log M) in the time-complexity.