Technical Report CS0250

Title: Should the Two-Headed Disk Be Greedy?
Authors: Micha Hofri
Abstract: We consider a disk with two movable arms, each of which can access all of its surface. Read/write requests arrive singly and are treated as they arrive (no queue is formed). The arms can move concurrently but not transmit simultaneously. We show that the policy that minimizes the mean seek time is to move to the required address the arm that is closest to it, while the other arm jockeys for optimal anticipatory position. This remains true when successive addresses are dependent and/or have different distributions.
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