TEKNOLOGI & ALGORITM PENJADWALAN DISK

Introduction

This tutorial focuses on disk scheduling technology and algorithms as discussed in the second meeting of the Operating Systems course. Understanding these concepts is crucial for optimizing how operating systems manage data on storage devices, improving overall system performance.

Step 1: Understanding Disk Scheduling

Disk scheduling refers to the methods used by an operating system to manage read and write requests to disk storage. The main goal is to minimize response time and maximize throughput.

• Key Concepts:

  • Throughput: The number of I/O operations completed in a given time period.
  • Latency: The time it takes for a specific I/O request to be completed.

• Importance: Effective disk scheduling can significantly impact system performance, especially in environments with high I/O demands.

Step 2: Exploring Scheduling Algorithms

There are several algorithms used for disk scheduling, each with its own advantages and disadvantages.

• First-Come, First-Served (FCFS):

  • Processes requests in the order they arrive.
  • Simple to implement but can lead to long wait times.

• Shortest Seek Time First (SSTF):

  • Selects the request closest to the current head position.
  • Reduces average seek time but may cause starvation for far requests.

• Elevator Algorithm (SCAN):

  • Moves the disk arm in one direction, servicing requests until it reaches the end, then reverses.
  • Provides a more uniform wait time compared to FCFS.

• Round Robin:

  • Each request gets an equal share of the disk time.
  • Fair and prevents starvation but may increase overall wait time.

Step 3: Analyzing Performance Metrics

When evaluating disk scheduling algorithms, consider the following performance metrics:

• Average Wait Time: The average time a request spends waiting in the queue.

• Average Turnaround Time: The total time taken from request submission to completion.

• Throughput: Total number of requests processed in a given time frame.

• Practical Tip: Use simulation tools to model different algorithms and analyze their performance under various workloads.

Step 4: Implementing Disk Scheduling in Practice

To implement these algorithms, you can write simple simulations or use existing tools. Here’s a basic framework for a disk scheduling simulation in Python:

def fcfs(requests):
    wait_time = 0
    for i in range(1, len(requests)):
        wait_time += abs(requests[i] - requests[i - 1])
    return wait_time

requests = [10, 20, 30, 40]
print("FCFS Wait Time:", fcfs(requests))

• Common Pitfalls:
  • Not considering the workload characteristics when choosing an algorithm.
  • Failing to account for the physical characteristics of the disk.

Conclusion

Understanding disk scheduling and its algorithms is essential for optimizing operating system performance. By exploring different methods like FCFS, SSTF, SCAN, and Round Robin, you can better manage data requests and improve efficiency. Experiment with simulations to find the best algorithm for your specific use case. As you move forward, consider deeper studies into how these algorithms affect system performance in real-world applications.