Illustrate rotational and average latency time in Database Management System
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Answer:
A second approach to reducing rotational latency of I/O accesses is to maintain two or more complete copies of data on the drive.1 For ease of discussion, dual copy is discussed here—extension to multiple copies is straightforward. Every sector of data is arranged such that it and its duplicate copy are located 180o out of phase with respect to each other. In other words, if a copy is currently under the head, its second copy is half a revolution away from the head. There are multiple ways with which this can be implemented. One method is to divide each track into two halves. The data recorded on the first half of a track is repeated in the second half. This means that each track should have an even number of sectors. With this approach, the number of logical tracks in a cylinder is not changed, but the capacity of each track is reduced by a factor of two.