Optimal Data Placement In

A problem inherent to the performance of disk systems is the data placement in cyinders in such a way that the seek time is minimized. If successive searchers are independent, then the optimal placement for conventional one-headed disk systems is the organ-pipe arrangement. According to this arrangement the most frequent cylinder is placed in the central location, while the less frequent cylinders are placed right and left alternatively. This paper proves that the optimal placement for two-headed disk systems is the "camel" arrangement, which may be viewed as two consecutive organ-pipe arrangements. It is also proved that, for a two-headed disk system with N = 2(2n + 1) cylinders, the total number of these optimal camel arrangements is exp~ (N/2 + 1). CR categories and subject descriptors: D.4.2. General terms : Algorithms, Performance. Additional key-words and phrases: Camel arrangement, Data placement, Organ-pipe arrangement, Seek distance, Two-headed disk.