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Observing the Effects of Multi-Zone Disks

Rodney Van Meter
Information Sciences Institute, University of Southern California


Current generations of hard disk drives use a technique known as zoned constant angular velocity (ZCAV), taking advantage of the geometry to increase total disk capacity by varying the number of disk sectors per track with the distance from the spindle. A side effect of this is that the transfer rate also varies with sector address. We analytically estimated and measured this effect on file system performance on a BSD Fast File System, showing a drop of roughly 25% in peak transfer rate depending on head position. We also show that, while ZCAV effects cannot be ignored, a simple linear model adequately estimates the performance from the few parameters normally available in disk drive spec sheets.

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Last changed: 22 Apr 2002 ml
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