Assignment 7 1. Briefly explain the differences between seek time and search tim
ID: 3710464 • Letter: A
Question
Assignment 7
1. Briefly explain the differences between seek time and search time. In your opinion, why do some people confuse the two?
2. Given the following characteristics for a magnetic tape using linear recording as described in this chapter:
Density = 1600 bpi
Speed = 1500 inches/second
Size = 2400 feet
Start/stop time = 4 ms
Number of records to be stored = 200,000 records
Size of each record = 160 bytes
Block size = 10 logical records
IBG = 0.5 inch
Find the following:
a. Number of blocks needed
b. Size of the block in bytes
c. Time required to read one block
d. Time required to write all of the blocks
e. Amount of tape used for data only, in inches
f. Total amount of tape used (data + IBGs), in inches
3. Given that it takes 1.75 ms to travel from one track to the next of a hard drive; that the arm is originally positioned at Track 15 moving toward the low- numbered tracks; and that you are using the LOOK, C-SCAN, and C-LOOK scheduling policy:
Compute the total seek time to satisfy the following requests—4, 40, 35, 11, 14, and 7. Assume all requests are initially present in the wait queue. (Ignore rotational time and transfer time; just consider seek time.)
4. Consider a virtual cylinder identical to the one shown in Figure 7.12 with the following characteristics: seek time is 4 ms/track, search time is 1.7 ms/sector, and data transfer time is 0.9 ms. Calculate the resulting seek time, earch time, data transfer time, and total time for the following Request List, assuming that the read/write head begins at Track 0, Sector 0. Finally, calculate the total time required to meet all of these requests.
Track
Sector
1
0
1
4
1
0
3
1
2
4
3
0
5. Using an identical environment to the previous question, calculate the resulting seek time, search time, data transfer time, and total time for the following:
Request List, assuming that the read/write head begins at Track 3, Sector 0.
Calculate the total time required.
Track
Sector
2
5
1
2
1
0
2
3
2
4
1
0
6. We received 1110110 1110110. A one bit error has occurred during the reception of the code word.
A. Find out the error bit?
B. What is the original data?
7. Describe how implementation of a RAID Level 1 system would be beneficial to a university payroll system. In your own words, describe the advantages and the disadvantages of such a system, if any, in that environment, and if appropriate, suggest an alternative RAID system and explain your reasoning.
Track
Sector
1
0
1
4
1
0
3
1
2
4
3
0
Explanation / Answer
Solution:
Note: The first and second question is done as per Chegg guidelines, please repost others.
The differences between seek time and search time is given below:
2)
a)
Number of blocks needed = Records needed / block size block size in terms of records = 200000/10 = 20000
b)
Size of the block in bytes:
Size of 1 record * block size in terms of records = 160*10 = 1600 bytes
c)
Time required to read a block
Size of 1 block = 1600 bytes 1 inch of the block
d)
The time required to write all the blocks:
1/1500 * 200000 = 133.33 seconds
e)
block size = 1600 bytes
First, we will calculate inches required per block
so density = 1600 bpi
1600 bytes requires 1 inch
so block size is also 1600 bytes which means 1 inch is required
amount of tapes used for data = 20, 000 inches
f)
we need to consider Interblock gap as well
so now a block will take 1 + IBG = 1 + 0.5 = 1.5 inches
total amount of tape required = 1.5 * 20000 = 30000 inches
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