I was review technical specifications for a Hitachi Disk drive E7K1000. First, I assume that 1D, 2D & 3D refer to the number of disks/platters that are in the physical drive. Is this correct? Assuming that is correct, then as the number of platters increases in the drive the average seek time goes down. This seems opposite to conventional thinking. Normally as you add additional heads (weight) this increases the inertia of the head assembly and it takes longer to move the head from one place to another. If you have ever had to work with any positioning system, you always want the positioner to be as light as possible to have the fastest switching time.
Can someone explain why they show a decreased seek time with more platters?
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http://www.hitachigst.com/tech/techlib.nsf/products/Deskstar_7K1000.B)
Link to specification PDF:
http://www.hitachigst.com/tech/techlib.nsf/techdocs/CF6C5D47F5BCE65B862574C1007E985D/$file/DS_CS_7K1000.B_Spec_rev3.01.pdf
Thanks!
AverageSeekTime.jpg
your assumption of head movements beeing a bit slower when having more heads is kinda correct, but on the other hand, 2 heads read twice as much data as 1 head, so being head for example, 20% slower, it has access to 100% more data, which is actual increase.
Also, more heads cover larger area, which is also increase in performace.
And least but not last, speed of read bytes per 1 disk revolution actuall doubles with each head, which is pure mathematical increase in data seek speed.