The problem of searching the set of keys in a file to find a key which is closest to a given query key is discussed. After “closest,” in terms of a metric on the the key space, is suitably defined, three file structures are presented together with their corresponding search algorithms, which are intended to reduce the number of comparisons required to achieve the desired result. These methods are derived using certain inequalities satisfied by metrics and by graph-theoretic concepts. Some empirical results are presented which compare the efficiency of the methods.

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This paper investigates the placement of data and parity on redundant disk arrays. Declustered organizations have been traditionally used to achieve fast reconstruction of a failed disk's contents. In previous work, Holland and Gibson identified six desirable properties for ideal layouts; however; no declustered layout satisfying all properties has been published in the literature.We present a complete, constructive characterization of the collection of ideal declustered layouts possessing all six properties. Given that ideal layouts exist only for a limited set of conjigurations, we also present two novel layout families. PRIME and RELPR can tolerate multiple failures in a wide variety of configurations with slight deviations from the ideal. Our simulation studies show that the new layouts provide excellent parallel access perjormance and reduced incremental loads during degraded operation, when compared with previously published layouts. For large accesses and under high loads, response times for the new layouts are typically smaller than those of previously published declustered layouts by a factor of 2.5.

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Abstract.A new interpolation-based order preserving hashing algorithm suitable for on-line maintenance of large dynamic external files under sequences of four kinds of operations insertion, update, deletion, and orthogonat range query is proposed. The scheme, an adaptation of linear hashing, requires no index or address directory structure and utilizes O(n) space for files containing n records; all of the benefits of linear hashing are inherited by this new scheme. File implementations yielding average successful search lengths much less than 2 and average unsuccessful search lengths much less than 4 for individual records are obtainable; the actual storage required is controllable by the implementor.