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Selecting a Disk-Scheduling Algorithm

_ Natural appeal in SSTF scheduling

_ SCAN and C-SCAN more appropriate for systems that place heavy load on disk

_ Performance heavily dependent on number and types of requests

_ Requests greatly influenced by file allocation method

·        Contiguously allocated file generates several requests close together on the disk

·        Linked allocation might include blocks that are scattered far apart

_ Location of directories and index blocks

·        Directory accessed upon the first reference to each file

·        Placing directories halfway between the inner and outer track of disk reduced head movement