I saw that I/O operations are faster on the beginning of a hard disk drive than on its end. Is that true and if so, why?
2 Answers
There is more data per track, just like on a record. As the read head moves inward it read less data per track and switches tracks more often.
Yes. Its true. In fact, one of the way some servers speed up processing is by taking advantage of this and "short stroking" the disk - ie only using the fast part.
In the case of the HD in question, the hard disk platter (ie spinning disk) is being read with the beginning on the outside and the end on the inside.
The circumference of the disk on the outside is much greater on the outside then on the inside - so it means that in the same amount of time much more information is underneath the reading head on the outer tracks (ie start) then on the innder tracks - so data is being read more quickly.
If you think of a merry-go-round, if you sit on the outside you will travel a much greater distance then if you sit near the center - same idea.
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But isn't that difference in circumference suppossed to be countered by a difference in data density ? Higher data density per area on the inner ring than outer ring , so per unit of time the read/write head reads equal amount of data irrespective of the position on disk ? Dec 30, 2014 at 9:23
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1Nope data density is uniformly, the highest possible for the largest possible hard drive. Dec 30, 2014 at 16:51