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Unformatted text preview: have a disk with 5 platters, 512 bytes per sector, 20,000 tracks per surface, and an average of 300 sectors per track. Then the capacity of the disk is: Disk capacity 512 bytes 300 sectors ¢ track sector 30,720,000,000 bytes 30.72 GB Notice that manufacturers express disk capacity in units of gigabytes (GB), where ½ ½¼ surfaces ¢ 20,000 tracks ¢ 2 platter ¢ 5 platters surface disk bytes. Aside: How much is a gigabyte? Unfortunately, the meanings of prefixes such as kilo (à ), mega (Å ) and giga ( ) depend on the context. For ½¼ ¾¼ ¿¼ measures that relate to the capacity of DRAMs and SRAMs, typically à ,Å and . For ¿ ,Å and measures related to the capacity of I/O devices such as disks and networks, typically à . Rates and throughputs usually use these prefix values as well. ¾ ¾ ½¼ ½¼ ¾ ½¼ ½¼ µ ½¼ Fortunately, for the back-of-the-envelope estimates that we typically rely on, either assumption works fine in pracand is small: ¾¼ tice. For example, the relative difference between ¾¼ ¿¼ ¿¼ . Sim...
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