When you first loaded files onto your new hard disk, they weren’t fragmented. Each whole file followed the last in consecutive disk clusters, lowest to highest. Your disk performance was never better.
When you began using those files — changing them, adding and deleting records and files — they were broken into smaller and smaller pieces scattered around the disk. That’s because your system writes each new record into the first empty slot it finds on the disk, even if it’s nowhere near the rest of the file.
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