Answers to Assignment 1 Questions

  1. Capacity of each DVD = 4.7GB; Amount to backup = 500GB; Number of disks needed = 500 / 4.7 = 106.383; Thus, 107 (4.7GB) DVDs are required to backup a full (500GB) hard drive.
  2. Amount to store per person = 40 bytes + 10 bytes + 9 bytes + 4 bytes = 63 bytes * number of people in the U.S. (310 million) = 19,530 million bytes (or 19.53GB). The data will fit on the 500GB hard drive, and will take up 500 / 19.53 = 25.6% of the available disk space.
  3. As we are starting a "new" disk access for each person, we are accessing each piece of data at a rate of 10ms. Thus, to access the individual tax data for each of the 310 million people, it will take 10ms (0.01 seconds) * 310 million = 3,100,000 seconds.
  4. As we are starting a "new" memory access for each person, we are accessing each piece of data at a rate of 100ns. Thus, to access the individual tax data for each of the 310 million people, it will take 100ns (0.0000001 seconds) * 310 million = 31 seconds.
  5. RAM is much faster than the hard disk, by a factor of 100,000.
  6. Using the table from Wikipedia (http://en.wikipedia.org/wiki/List_of_device_bit_rates#Modems.E2.80.94narrow_and_broadband), and as no specification was required in regards to the version or type of modem/DSL, the speeds used for this part are as follows:
    Dial-up modem (56 kbit/s, or 5.6 kB/s) = 89,285,714.285714 seconds
    ADSL2+ (24,576 kbit/s, or 3,072 kB/s) = 1,627,604.16 seconds
    Overnight mail = The entire hard drive will arrive at the friend's house the next day; however, if we are restricted to only sending one byte at a time (and not the drive), then it will take 500,000,000,000 days for all the data to arrive at the friend's house (unless, you send all 500,000,000,000 bytes at the same time in different packages; in which case it will still only take one day).

*Conversion lookup on http://www.calculateme.com/Time/index.htm