Typical desktop hard disk drives from mid-to-late 1990s revolved at 5400 rpm and had transfer rates from 3 MB / s to 10 MB / s or more, and average seek times from 20 ms to 14 ms or less.
12.
This degrades performance by increasing the average seek time : some head movements are forced to wait an additional disk rotation before accessing data because the head was unable to move to the target position during the first rotation due to velocity limits.
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An HDD's " Average Access Time " is its average seek time which technically is the time to do all possible seeks divided by the number of all possible seeks, but in practice is determined by statistical methods or simply approximated as the time of a seek over one-third of the number of tracks.
