Dale - Computer Science Illuminated 391

Dale - Computer Science Illuminated 391 - 49, 91, 22, 61,...

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364 Chapter 11 File Systems and Directories Figure 11.6 A magnetic disk drive Block Track Sector (b) A single disk (a) A hard disc drive Arm Spindle Cylinder Read/write head At any point in time, a disk drive may have a set of outstanding requests that must be satisfied. For now, we consider only the cylinder (the parallel concentric circles) to which the requests refer. A disk may have thousands of cylinders. To keep things simple, let’s also assume a range of 100 cylin- ders. Suppose at a particular time the following cylinder requests have been made, in this order:
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Unformatted text preview: 49, 91, 22, 61, 7, 62, 33, 35 Suppose also, that the read/write heads are currently at cylinder 26. The question is now: To which cylinder should the disk heads move next? Different algorithms produce different answers to that question. First-Come, First-Served Disk Scheduling In Chapter 10 we examined a CPU scheduling algorithm called first-come , first-served (FCFS) . An analogous algorithm can be used for disk scheduling. It is one of the easiest to implement, though not usually the most efficient....
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This note was uploaded on 01/13/2011 for the course CSE 1550 taught by Professor Marianakant during the Fall '10 term at York University.

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