Register

Test by Bikram | Operating Systems | Test 2 | Question: 11

• retagged by
1,725 views
0 0 votes

Suppose that a disk drive has $5000$ cylinders, numbered $0$ to $4999$. The drive is currently serving a request at cylinder $143$, and the previous request was at cylinder $125$. The queue of pending requests, in FIFO order, is $86, \ 1470, \ 913, \ 1774,\  948, \ 1509, \ 1022, \ 1750, \ 130$.

Starting from the current head position, what is the total distance (in cylinders) that the disk arm moves to satisfy all the pending requests, for each of the following disk – scheduling algorithms?

FCFS
SSTF
SCAN

  1. $7081, \ 1745, \ 9769$
  2. $7081, \ 1745, \ 7081$
  3. $1745, \ 1004, \ 9600$
  4. $9769, \ 1745, \ 7081$

1 Answer

Best answer
2 2 votes
The total seek time is sum of difference between successive head positions.
 A  The FCFS schedule is 143, 86, 1470, 913, 1774, 948, 1509, 1022, 1750, 130. The total seek distance  is 7081.

 B  The SSTF schedule is 143, 130, 86, 913, 948, 1022, 1470, 1509, 1750, 1774. The total seek distance is 1745.

 C  The SCAN schedule is 143, 913, 948, 1022, 1470, 1509, 1750, 1774, 4999, 130, 86. The total seek distance is 9769 .
• selected by
Voting & Accepting an answer helps improve the community
Answer:
← Previous · Test by Bikram | Ope...Next → · Test by Bikram | Ope...
← Previous in category · Test by Bikram | Ope...Next in category → · Test by Bikram | Ope...
Position:
Show:

Related questions

1 1 vote
1 answers 1 answer
1.4k
1.4k views
Bikram asked Dec 26, 2016
1,414 views
Test by Bikram | Operating Systems | Test 2 | Question: 21
Suppose the disk drive has $200$ cylinders ( numbered $0$ to $199$). The drive is currently serving the request at cylinder $53$. The previous request was at cylinder $2...
2 2 votes
1 answers 1 answer
635
635 views
Bikram asked Dec 26, 2016
635 views
Test by Bikram | Operating Systems | Test 2 | Question: 30
Consider the following 3 processes with 3 binary semaphores with initial values $S_{0}=0, S_{1}=0, S_{2}=1$$$ \begin{array}{|c|c|c|} \hline \textbf{P} & \textbf{Q} & \tex...
2 2 votes
3 answers 3 answers
3.1k
3.1k views
Bikram asked Dec 26, 2016
3,137 views
Test by Bikram | Operating Systems | Test 2 | Question: 29
In a paged memory, the page hit ratio is $0.35$. The time required to service the page fault is $100$ ns. Time required to access a page in primary memory is $10$ ns.The ...
8 8 votes
1 answers 1 answer
1.5k
1.5k views
Bikram asked Dec 26, 2016
1,524 views
Test by Bikram | Operating Systems | Test 2 | Question: 28
Consider a program to be run on a computer system in round-robin CPU scheduling. The size of the program is $100K$. It is given that the hard disk has a transfer rate of ...