Drive a: • drive diameter: 3.5" • platters: 2 • rpm: 7,500 • exterior color: silver • average time needed to move the read heads to a specific track (seek time): 7ms • rate at which data passes under the read heads: 40 mb/s • rate at which the hard drive communicates with the computer: 100 mb/s
drive b: • drive diameter: 2.5" • platters: 4 • rpm: 10,000 • exterior color: blue • average time needed to move the read heads to a specific track (seek time): 4ms • rate at which data passes under the read heads: 90 mb/s. the rate at which the hard drive communicates with the computer: 200 mb/s
assume that the os requests a read of some block of data from one track on a drive. assume the drive controller will read the entire block of data from the disk, then begin transmitting the data back to the os. answer the following questions twice, once for drive a and once for drive b.
a. what is the average latency for reading a 1024 byte block of data? b. what is the minimum latency for reading a 2048 byte block of data? c. for each drive, determine the dominant factor that affects latency. specifically, if you could make an improvement to any one aspect of that drive, what would you improve and why? if there is no dominant factor, explain why. hints: simply sum up the latencies imposed by seeks, rotational delay, time to read the data from disk into the controller, and time to transmit the data from the controller to the main memory. (these correspond to some of the numbers given in the data tables.) the controller would impose a small logical overhead, do not include this. for minimums, assume the disk mechanisms are in the ideal positions for the read.