Secondary Storage

1. An old model of hard drives for IBM mainframe systems consisted of 9 disk platters, in which the bottom disk was not used to store actual file data, but as a mechanism to increase data reliability. What might be stored on the bottom disk?

2. To minimize head movement, hard disks often place related file data on tracks of the same cylinder rather than on adjacent tracks of the same surface. Why does this reduce head movement?

3. You have a disk drive with the following characteristics:
   • seek time: 30 ms
   • rotational delay (latency): 10 ms
   • transfer rate: 5 Kbytes/ms
   On average, how long would it take to read 500 bytes from this disk?

4. Why is it necessary, in general, for a checksum function to produce different values for different inputs?

5. Is binary or character-based I/O more space-efficient for the storage of numbers? Explain.