Figure 2 – Read throughput variation across the Quantum Atlas 10K surface. The read throughput on the inner band of the media is significantly less than the outer band. The inner band on the Atlas 10K has 35% less throughput than on the outer band. Measurements taken on the Fireball lct08 showed its inner band had 40% less throughput than on its outer band.
Zoned Disk and Variable Media Rates
Modern disks are zoned: tracks have a variable number of sectors and therefore a variable size rather than a fixed size. Each track’s size is a function of its circumference. Since tracks on the outer edge of the media have a larger circumference than tracks on the inner edge, outer tracks have more bits traveling under the disk head per second than inner tracks due to the disk’s constant angular velocity. The Ziff Davis WinBench 99 was used to generate Figure 2 that shows a throughput map of the disk as the head is moved from the outer to the inner tracks [ZD]. The stair stepping is due to banding on the media. Each band has the same number of sectors per track. Within each band, the throughput remains the same. From band to band however, the sectors per track changes, resulting in a sudden change in throughput. Figure 2 also shows that there is considerable variance among read speeds ranging 10%.
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