Quorums from difference covers

Maekawa considered a simple but suboptimal grid-based quorum generation sch eme in which N sites in the network are logically organized in the form of a root N x root N grid, and the quorum sets are row-column pairs. Even thou gh the quorum size 2 root N of the grid scheme is twice as large as finite projective plane with optimal sized quorums, it has the advantage of being simple and geometrically evident. Agrawal, Egecioglu, and El Abbadi propose d another grid based scheme producing quorums of size root 2N. In this note , a very simple construction is given to produce a system of quorums of siz e root 1.5N. These can be generated efficiently. (C) 2000 Elsevier Science B.V. All rights reserved.