If there is a magnetic disk as following:
Average seek time: 12 ms
Rotation rate: 3600 RPM
Transfer rate: 3.5 MB/second
Number of sectors per track: 64
Sector size: 512 bytes
Controller overhead: 5.5 ms
What's the average time to read a single sector? I'm not sure how/why 2 parts are calculated.
We need to know:
Seek time: 12 ms Average rotational delay: The answer here should be 8.3 but why? 60000/7200 would indeed give me 8.3 but why do I need to double the 3600? Transfer time: Not sure what to do here. Sector size is 512 bytes and rate is 3.5 MB/sec -- what do I need to calculate here? Overhead: 5.5ms
Disk Access time: I believe the answer is about 25ms
Resulting from (seek time) 12 ms + (average rotational delay) 8.3 + (transfer time) ? + (overhead) 5.5ms.