Operating System Tutorial

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Difference Between Multi-programming and Multitasking Difference between C-LOOK and C-SCAN Difference between Rotational Latency and Disk Assess Time Trap vs Interrupt Difference between C-SCAN and SSTF Difference between SCAN and FCFS Difference between Seek Time and Disk Access Time Difference between SSTF and LOOK Difference between Process and Program in the Operating System Difference between Protection and Security in Operating System

How To

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What is Kernel and Types of Kernel What is DOS Operating System What is Thread and Types of Thread What is Process Scheduler and Process Queue What is Context Switching What is CPU Scheduling What is Producer-Consumer Problem What is Semaphore in Operating System Monitors in Operating System What is Deadlock What is Paging and Segmentation What is Demand Paging What is Virtual Memory What is a Long term Scheduler What is Page Replacement in Operating System What is BSR Mode What is Convoy Effect What is Job Sequencing in Operating System Why is it critical for the Scheduler to distinguish between I/O-bound and CPU-bound programs Why is there a Need for an Operating System


Process Management Process State Scheduling Algorithm FCFS (First-come-First-Serve) Scheduling SJF (Shortest Job First) Scheduling Round-Robin CPU Scheduling Priority Based Scheduling HRRN (Highest Response Ratio Next) Scheduling Process Synchronization Lock Variable Mechanism TSL Mechanism Turn Variable Mechanism Interested Variable Mechanism Deadlock Avoidance Strategies for Handling Deadlock Deadlock Prevention Deadlock Detection and Recovery Resource Allocation Graph Banker’s Algorithm in Operating System Fixed Partitioning and Dynamic Partitioning Partitioning Algorithms Disk Scheduling Algorithms FCFS and SSTF Disk Scheduling Algorithm SCAN and C-SCAN Disk Scheduling Algorithm Look and C-Look Disk Scheduling Algorithm File in Operating System File Access Methods in Operating System File Allocation Method Directory Structure in Operating System N-Step-SCAN Disk Scheduling Feedback Queue in Operating System Contiguous Memory Allocation in Operating System Real-time Operating System Starvation in Operating System Thrashing in Operating System 5 Goals of Operating System Advantages of Operating System Advantages of UNIX Operating System Bit Vector in Operating System Booting Process in Operating System Can a Computer Run Without the Operating System Dining Philosophers Problem in Operating System Free Space Management in Operating System Inter Process Communication in Operating System Swapping in Operating System Memory Management in Operating System Multiprogramming Operating System Multitasking Operating Systems Multi-user Operating Systems Non-Contiguous Memory Allocation in Operating System Page Table in Operating System Process Scheduling in Operating System Segmentation in Operating System Simple Structure in Operating System Single-User Operating System Two Phase Locking Protocol Advantages and Disadvantages of Operating System Arithmetic operations in binary number system Assemblers in the operating system Bakery Algorithm in Operating System Benefits of Ubuntu Operating System CPU Scheduling Criteria in Operating System Critical Section in Operating System Device Management in Operating System Linux Scheduler in Operating System Long Term Scheduler in Operating System Mutex in Operating System Operating System Failure Peterson's Solution in Operating System Privileged and Non-Privileged Instructions in Operating System Swapping in Operating System Types of Operating System Zombie and Orphan Process in Operating System 62-bit operating system Advantages and Disadvantages of Batch Operating System Boot Block and Bad Block in Operating System Contiguous and Non - Contiguous Memory Allocation in Operating System Control and Distribution Systems in Operations Management Control Program in Operating System Convergent Technologies in Operating System Convoy Effect in Operating System Copy Operating Systems to SSD Core Components of Operating System Core of UNIX Operating System Correct Value to return to the Operating System Corrupted Operating System Cos is Smart Card Operating System Cosmos Operating Systems Examples Generation of Operating System Hardware Solution in Operating System Process Control Block in Operating System Function of Kernel in Operating System Operating System Layers History of Debian Operating Systems Branches and Architecture of Debian Operating Systems Features and Packages of Debian Operating Systems Installation of Operating System on a New PC Organizational Structure and Development in Debian Operating Systems User Interface in Operating System Types Of Memory in OS Operating System in Nokia Multilevel Paging in OS Memory Mapping Techniques in OS Memory Layout of a Process in Operating System Hardware Protection in Operating System Functions of File Management in Operating System Core of Linux Operating System Cache Replacement Policy in Operating System Cache Line and Cache Size in Operating System What is Memory Mapping? Difference Between Network Operating System And Distributed Operating System What is the difference between a Hard link and a Soft Link? Principles of Preemptive Scheduling Process Scheduling Algorithms What is NOS? What is the Interrupt I/O Process? What is Time Sharing OS What is process termination? What is Time-Sharing Operating System What is Batch File File system manipulation What is Message-passing Technique in OS Logical Clock in Distributed System

Disk Scheduling Algorithms

Disk Scheduling Algorithms

Disk scheduling algorithms are the algorithms that are used for scheduling a disk. Generally, the scheduling refers to a time-table for completing any task or a job. With the help of the operating system, disk scheduling is performed. We use disk scheduling to schedule the Input/output requests that arrive for the disk.  

In other words, we can define disk scheduling as a method that is used by the OS (operating system) to schedule the next upcoming requests. Disk Scheduling is also called Input/output scheduling.

Disk scheduling is important because of the following reasons:

  1. The slowest part of the computer system is the hard drive. So, to access the hard drive conveniently or effectively, we need disk scheduling.
  2. There may be chances that two or more requests can be distant from each other. Therefore, more disk arm movement can happen. Thus, we need disk scheduling for such handling case
  3. Sometimes, there are various I/O requests which arrive from the different processes. But at a time, the disk controller can only serve one I/O request. So, in this way, the other requests have to wait in the waiting queue, and scheduling is needed for those processes that are waiting in the waiting queue.

Objective of Disk Scheduling Algorithm

The objectives of the disk scheduling algorithm are:

  1. Less traveling head time.
  2. Fairness.
  3. Throughput must be high.

Purpose of Disk Scheduling

The purpose of disk scheduling is to choose a disk request from the input/output requests queue and then scheduling the remaining request means which has to be processed

Basic Terms

There are various types of disk scheduling algorithms, but before discussing them, we need to know various essentials terms which are given below:

  1. Seek Time: - Seek time is defined as the time which is used to find the disk arm to a stated track where the data must be read and write. The better disk algorithm is one that gives less average seek time.
  2. Transfer Time: - Transfer time is defined as the time which is used for data transfer. Transfer time depends on two things:
  3. Bytes which we have to transfer

2) The rotation speed of the disk.

  •  Rotational Latency: - Rotational latency means the time which is needed to rotate the desired sector into a position so that a read/write heads can be accessed. The better disk scheduling algorithm is that which takes less rotational latency.
  • Disk Access Time: - We can define disk access time as:
Disk Scheduling Algorithms
  • Disk Response Time: - Disk response time is defined as the average time, which is used by an individual request, waiting for input/output operations. The best scheduling algorithm is one that gives less variance response.

Disk Scheduling Algorithms

There are different types of disk scheduling algorithms. Each algorithm contains its own benefits and drawbacks.

  1. FCFS (first-come-first-serve) disk scheduling algorithm
  2. SSTF (shortest seek time first) disk scheduling algorithm
  3. SCAN disk scheduling algorithm
  4. C-SCAN disk scheduling algorithm
  5. LOOK disk scheduling algorithm
  6. C-LOOK disk scheduling algorithm.