When a data file is replicated at more than one site, we are interested in detecting corruption by comparing the multiple copies. In order to reduce the amount of messaging for large files, techniques based on page signatures and combined signatures have been explored. However, for 3 or more sites, the known methods assume that the number of corrupted page copies to be at most [M/2]-1, where M is the number of sites. We point out that this assumption is unrealistic and the corresponding methods are unnecessarily pessimistic. In this paper, we replace this assumption by another assumption which we show to be reasonable. Based on this assumption, we derived a distributed algorithm which in general achieves better performance than previously known results. Our system model is also more refined than previous work.
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