Why disk scheduling reduces seek time in Operating Systems - See It in Action

Why Disk Scheduling Reduces Seek Time

📖 Scenario: Imagine you work in a library where you need to fetch books from different shelves. Moving from one shelf to another takes time. You want to find a way to pick books in an order that saves your walking time.

🎯 Goal: Build a simple example that shows how ordering requests (disk scheduling) helps reduce the total movement (seek time) when accessing data on a disk.

📋 What You'll Learn

Create a list of disk requests representing positions on the disk.

Set a starting position of the disk head.

Apply a simple scheduling method to reorder requests to minimize movement.

Calculate the total seek time based on the reordered requests.

💡 Why This Matters

🌍 Real World

Disk scheduling is used in computers to decide the order of reading or writing data on a hard drive, which helps the system work faster and more efficiently.

💼 Career

Understanding disk scheduling is important for roles in system administration, software development, and IT support, where optimizing hardware performance is valuable.

1

Create the list of disk requests

Create a list called requests with these exact disk positions: 95, 180, 34, 119, 11, 123, 62, 64.

Operating Systems

# Create the list of disk requests
# Your code here

Need a hint?

Use square brackets to create a list and separate numbers with commas.

2

Set the starting position of the disk head

Create a variable called head_position and set it to 50 to represent the current position of the disk head.

Operating Systems

requests = [95, 180, 34, 119, 11, 123, 62, 64]
# Set the starting position of the disk head
# Your code here

Need a hint?

Use a simple assignment to create the variable.

3

Reorder requests to reduce seek time

Create a new list called scheduled_requests that contains the requests sorted by their distance from head_position. Use the sorted() function with a key that calculates the absolute difference from head_position.

Operating Systems

requests = [95, 180, 34, 119, 11, 123, 62, 64]
head_position = 50
# Reorder requests to minimize seek time
# Your code here

Need a hint?

Use sorted() with a lambda function to sort by distance.

4

Calculate total seek time after scheduling

Create a variable called total_seek_time and set it to 0. Then use a for loop with variables i from 0 to len(scheduled_requests) - 1 to add the absolute difference between consecutive requests (starting from head_position) to total_seek_time. Use previous_position to track the last position, starting with head_position.

Operating Systems

requests = [95, 180, 34, 119, 11, 123, 62, 64]
head_position = 50
scheduled_requests = sorted(requests, key=lambda x: abs(x - head_position))
# Calculate total seek time
# Your code here

Need a hint?

Use a loop to add distances between each request and the previous position.