Given a magnetic hard drive with the following characteristics, what is the aver

Question

Given a magnetic hard drive with the following characteristics, what is the average time to read 8KB of data from 16 consecutive sectors?

Please explain, i realize the formula is T = Tseek + Trotate + Ttransfer + Tcontroller however I get confused when finding Tseek and rotate even.

Given a magnetic hard drive with the following characteristics, what is the average time to read 8KB of data from 16 consecutive sectors? Please explain, i realize the formula is T = Tseek + Trotate + Ttransfer + Tcontroller however I get confused when finding Tseek and rotate even.

Explanation / Answer

Hi there,

Tseek = Average seek time 12ms

Trotate = 3600 RPM / 60 seconds = 60rev/s

= 1sec / 60rev = 16.6ms/rev

Iin fact the HD will never do a complete rotation, if the block is further that half of the disk, it will go the other way. So, you have to divide this number by 2.

= 16.6ms / 2 = 8.3ms

T = 12ms (average seek time) + 8.3ms (rotation speed) + 0.14 (0.5 KB / 3.5MB/s) + 5.5ms (controller time) = 25.94ms/block of 512bytes

= 25.94 * 16 = 415.04 ms to read all blocks

Hope this help !!

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