Input/Output Scheduling: Enhance System Performance with Efficient Algorithms

Question 1

How do simulations contribute to evaluating I/O scheduling algorithms? Explain how simulations provide insights that theoretical analysis might miss.

Accepted Answer

Simulations allow testing algorithms in controlled environments, revealing performance aspects that theoretical models may not capture.

Answer

Simulations are limited to simple algorithms and cannot handle the complexity of real-world I/O systems.

Answer

Simulations completely replace theoretical analysis, providing more accurate results.

Answer

Simulations are only used to compare different I/O scheduling algorithms.

Question 2

Which of the following is not an I/O scheduling algorithm commonly used in operating systems?

Accepted Answer

Round Robin

Answer

First Come First Serve (FCFS)

Answer

Shortest Seek Time First (SSTF)

Answer

Elevator Algorithm (SCAN)

Question 3

FCFS stands for:

Accepted Answer

First Come First Served

Answer

Fast Clock Fast Service

Answer

File Control File System

Answer

First Card First Served

Question 4

SSTF considers the location of which of the following when scheduling disk I/O requests?

Accepted Answer

Closest request

Answer

Previous request

Answer

Current request

Answer

Next request

Question 5

Which I/O scheduling algorithm is best suited for systems with multiple active processes that require fair access to disk resources?

Accepted Answer

Round Robin

Answer

FCFS

Answer

SSTF

Answer

SCAN

Question 6

Which scheduling discipline is considered non-preemptive, meaning that once a process starts executing, it cannot be interrupted by other processes until it completes its I/O operation?

Accepted Answer

FCFS

Answer

Shortest Job First

Answer

Round Robin

Answer

Priority Scheduling

Question 7

Which of the following factors does not directly affect the performance of an I/O scheduling algorithm?

Accepted Answer

CPU speed

Answer

Disk seek time

Answer

Number of I/O requests

Answer

Disk size

Question 8

What is the primary advantage of using the SSTF algorithm for I/O scheduling?

Accepted Answer

Reduced average seek time

Answer

Improved disk throughput

Answer

Increased memory utilization

Answer

Enhanced device utilization

Question 9

In FCFS, requests are processed in the order they:

Accepted Answer

Arrive

Answer

Complete

Answer

Are prioritized

Answer

Are preempted

Question 10

SSTF algorithm aims to:

Accepted Answer

Minimize seek time

Answer

Maximize throughput

Answer

Reduce latency

Answer

Increase fairness

Question 11

Priority-based I/O scheduling algorithms are suitable when:

Accepted Answer

Requests have varying importance

Answer

Requests arrive in bursts

Answer

The system is heavily loaded

Answer

Fairness is not a concern

Question 12

In a heavily loaded system, which I/O scheduling algorithm is likely to have the worst performance?

Accepted Answer

FCFS

Answer

SSTF

Answer

SCAN

Answer

Priority

Question 13

Which algorithm typically minimizes the average waiting time for requests close to the current head position?

Accepted Answer

SSTF

Answer

FCFS

Answer

SCAN

Answer

C-SCAN

Question 14

Which factor does not directly influence the performance of an I/O scheduling algorithm?

Accepted Answer

Processor speed

Answer

Request arrival rate

Answer

Request size

Answer

Disk seek time

Question 15

Which of the following is irrelevant when selecting an appropriate I/O scheduling algorithm?

Accepted Answer

Current time of day

Answer

Type of storage device

Answer

Number of I/O requests

Answer

Disk access patterns

Question 16

Which of the following is a potential limitation of the C-SCAN algorithm?

Accepted Answer

Increased seek time for requests at the beginning and end of the disk

Answer

Complex implementation

Answer

Inefficient handling of I/O bursts

Answer

High overhead due to disk arm movement

Question 17

What is the fundamental distinction between the SCAN and C-SCAN algorithms?

Accepted Answer

SCAN moves in both directions, while C-SCAN moves only in one direction

Answer

C-SCAN is more efficient in high I/O workload scenarios

Answer

SCAN handles requests outside of the current track, while C-SCAN does not

Answer

C-SCAN has a lower average seek time compared to SCAN

Question 18

Which of the following metrics is not used to assess the performance of I/O scheduling algorithms?

Accepted Answer

CPU utilization

Answer

Average seek time

Answer

Disk utilization

Answer

Throughput

Question 19

What is the primary objective of I/O scheduling?

Accepted Answer

Minimizing disk head movement

Answer

Maximizing data transfer rates

Answer

Preventing data loss

Answer

Reducing processor idle time

Question 20

In which data structure are I/O requests typically organized?

Accepted Answer

Queue

Answer

Stack

Answer

List

Answer

Array

Question 21

Which acronym stands for First-Come First-Served I/O scheduling algorithm?

Accepted Answer

FCFS

Answer

SSTF

Answer

SCAN

Answer

CSCAN

Question 22

What is the primary distinction between SCAN and CSCAN algorithms?

Accepted Answer

SCAN operates bidirectionally, while CSCAN operates unidirectionally.

Answer

CSCAN operates bidirectionally, while SCAN operates unidirectionally.

Answer

SCAN is non-preemptive, whereas CSCAN is preemptive.

Answer

CSCAN is non-preemptive, whereas SCAN is preemptive.

Question 23

Which I/O scheduling algorithm gives priority to the request closest to the current head position?

Accepted Answer

Shortest Seek Time First (SSTF)

Answer

First Come First Serve (FCFS)

Answer

SCAN

Answer

C-SCAN

Question 24

In which situation is FCFS the most suitable I/O scheduling algorithm?

Accepted Answer

When requests are evenly distributed across the disk

Answer

When requests are clustered together

Answer

When the average seek time is minimal

Answer

When the system is heavily loaded

Question 25

How does SCAN differ from C-SCAN?

Accepted Answer

SCAN services requests in both directions, while C-SCAN serves requests in one direction only

Answer

SCAN is more efficient for fragmented disk environments, while C-SCAN is more efficient for contiguous disk environments

Answer

C-SCAN optimizes for average seek time, while SCAN optimizes for maximum seek time

Answer

There is no difference between SCAN and C-SCAN

Question 26

In a disk system with 200 cylinders, the current head position is at cylinder 50. A request arrives to access cylinder 180. Calculate the seek time using FCFS.

Accepted Answer

130 cylinders

Answer

50 cylinders

Answer

180 cylinders

Answer

200 cylinders

Question 27

Which of the following factors does NOT influence the selection of an I/O scheduling algorithm?

Accepted Answer

User preferences

Answer

Disk access patterns

Answer

Disk size

Answer

Application requirements

Question 28

What is an advantage of using SSTF?

Accepted Answer

Minimized average seek time

Answer

Increased throughput

Answer

Reduced disk fragmentation

Answer

Improved I/O device reliability

Question 29

How does C-SCAN differ from SCAN in terms of disk head movement?

Accepted Answer

C-SCAN moves the head in one direction only, while SCAN moves the head in both directions

Answer

SCAN moves the head in one direction only, while C-SCAN moves the head in both directions

Answer

C-SCAN moves the head in a circular motion, while SCAN moves the head in a linear motion

Answer

There is no difference in disk head movement between C-SCAN and SCAN

Question 30

How do emerging storage technologies, such as NVMe and Optane, influence the design and implementation of I/O scheduling algorithms?

Accepted Answer

Emerging storage technologies offer both challenges and opportunities for designing and implementing I/O scheduling algorithms.

Answer

Emerging storage technologies have no significant impact on I/O scheduling algorithm design.

Answer

Emerging storage technologies always simplify and enhance I/O scheduling algorithms.

Answer

The choice of I/O scheduling algorithm is unaffected by the storage technology employed.

Question 31

Which I/O scheduling algorithm prioritizes disk requests that are closest to the current read/write head position?

Accepted Answer

Shortest Seek Time First (SSTF)

Answer

First-Come First-Served (FCFS)

Answer

Scan

Answer

Circular Scan

Question 32

Which drawback is commonly associated with using the FCFS I/O scheduling algorithm?

Accepted Answer

Potential for starvation, where some requests may wait indefinitely for service

Answer

Complex implementation

Answer

Inefficient disk bandwidth utilization

Answer

High average seek time

Question 33

Which I/O scheduling algorithm moves the disk head back and forth across the disk surface, servicing requests in both directions?

Accepted Answer

Scan

Answer

FCFS

Answer

SSTF

Answer

C-SCAN

Question 34

Which I/O scheduling algorithm is a variant of Scan that only scans in a single direction?

Accepted Answer

C-SCAN

Answer

SCAN

Answer

FCFS

Question 35

In which scenario would the SSTF algorithm be most suitable?

Accepted Answer

When disk requests are clustered together in specific regions of the disk

Answer

When disk requests are evenly distributed across the disk

Answer

When disk access time is the highest priority

Answer

When the disk is heavily fragmented

Question 36

Which factor is not typically considered when evaluating the performance of I/O scheduling algorithms?

Accepted Answer

Network speed

Answer

Disk access time

Answer

Disk fragmentation

Answer

Disk queue length

Question 37

Which I/O scheduling algorithm is specifically designed for real-time systems?

Accepted Answer

Earliest Deadline First (EDF)

Answer

FCFS

Answer

SSTF

Answer

SCAN

Question 38

What is the primary objective of I/O scheduling algorithms?

Accepted Answer

To minimize the total seek time required to service disk requests

Answer

To prevent starvation of requests

Answer

To process the maximum number of I/O requests

Answer

To maximize the disk bandwidth utilization

Question 39

A disk drive with a queue of requests (cylinder numbers) 98, 183, 37, 122, 14, 124. What is the order of requests processed using the FCFS algorithm?

Accepted Answer

98, 183, 37, 122, 14, 124

Answer

14, 98, 122, 124, 37, 183

Answer

14, 37, 98, 122, 124, 183

Answer

37, 14, 98, 122, 124, 183

Question 40

Which I/O scheduling algorithm is known for its potential to cause starvation for requests at the edges of the disk?

Accepted Answer

SCAN

Answer

C-SCAN

Answer

FCFS

Answer

SSTF

Question 41

Which of the following I/O scheduling algorithms is considered to be most fair?

Accepted Answer

FCFS (First Come First Served)

Answer

SSTF (Shortest Seek Time First)

Answer

SCAN

Answer

C-SCAN

Question 42

What is the primary goal of I/O scheduling algorithms?

Accepted Answer

To optimize disk utilization and minimize average response time.

Answer

To ensure all requests are processed in a strict order.

Answer

To maximize the number of requests served per second.

Question 43

In a scenario where disk requests are arriving at a high rate, which I/O scheduling algorithm is generally considered most efficient?

Accepted Answer

SCAN

Answer

FCFS

Answer

C-SCAN

Answer

SSTF

Question 44

The C-SCAN algorithm is a modified version of the SCAN algorithm. What is the key difference between the two?

Accepted Answer

C-SCAN only scans in one direction, preventing starvation of requests at the other end of the disk.

Answer

C-SCAN is designed for high-throughput systems, while SCAN is suitable for low-latency scenarios.

Answer

C-SCAN prioritizes the closest request, while SCAN considers the overall movement direction.

Question 45

Which of the following is NOT a factor that influences the performance of an I/O scheduling algorithm?

Accepted Answer

The type of CPU being used.

Answer

The disk access time.

Answer

The disk arm movement speed.

Answer

The number of pending requests.

Question 46

In a system with a high load of small file requests, which I/O scheduling algorithm would likely be the most suitable?

Accepted Answer

SSTF (Shortest Seek Time First)

Answer

FCFS (First Come First Served)

Answer

SCAN

Answer

C-SCAN

Question 47

What is the primary drawback of the FCFS (First Come First Served) I/O scheduling algorithm?

Accepted Answer

It can lead to inefficient disk utilization and high average response time, especially when requests are clustered at distant locations.

Answer

It can cause starvation for requests that are far away from the current head position.

Question 48

Which I/O scheduling algorithm grants service to requests in the order they arrive?

Accepted Answer

FCFS

Answer

SSTF

Answer

SCAN

Answer

CSCAN

Question 49

Which of the following statements accurately describes the Shortest Seek Time First (SSTF) algorithm?

Accepted Answer

It selects the request with the shortest seek time from the current head position.

Answer

It prioritizes requests with the largest file sizes.

Answer

It ensures equal waiting times for all requests.

Question 50

A disk with a seek time of 10 ms is using SCAN algorithm. The disk head is currently at track 60 and the requests are queued as [40, 80, 20, 100, 25]. What is the total seek time incurred?

Accepted Answer

150 ms

Answer

250 ms

Answer

200 ms

Answer

300 ms

Question 51

Which I/O scheduling algorithm is most likely to be used for interactive systems?

Accepted Answer

FCFS

Answer

CSCAN

Answer

SCAN

Answer

SSTF

Question 52

What is the main drawback of using the FCFS algorithm?

Accepted Answer

Starvation of certain requests, especially those with long waiting times.

Answer

High seek time due to non-optimized request ordering.

Answer

Complexity in implementation and maintenance.

Question 53

Which I/O scheduling algorithm is designed to minimize the average rotational latency of requests?

Accepted Answer

CSCAN

Answer

SSTF

Answer

SCAN

Answer

FCFS

Question 54

In which scenario would the SSTF algorithm perform better than the SCAN algorithm?

Accepted Answer

When requests are clustered in specific areas of the disk.

Answer

When requests are uniformly distributed across the disk.

Answer

When seek time is a more significant concern than rotational latency.

Question 55

Which of the following is NOT a factor to consider when selecting an I/O scheduling algorithm?

Accepted Answer

Disk size

Answer

Request arrival rate

Answer

Seek time

Answer

Application requirements

Question 56

What is the purpose of a disk scheduler?

Accepted Answer

To manage the order in which disk access requests are served.

Answer

To control the physical movement of the disk head.

Answer

To prevent data loss in case of disk failure.

Question 57

Which I/O scheduling algorithm is most suitable for systems with multiple disk drives?

Accepted Answer

None of the above

Answer

SCAN

Answer

SSTF

Answer

FCFS