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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

How to implement Monitors using Semaphores How to Install a Different Operating System on a PC


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?

Difference between Rotational Latency and Disk Assess Time in Disk Scheduling

Disk scheduling is used by operating systems to arrange the arrival of I/O requests to the disc. Disk scheduling is necessary because several I/O requests may occur from various processes, and the disc controller can only service one I/O request at a time. As a result, further I/O requests must wait in the queue and be scheduled. The phrases seek time, rotational latency, transfer time, and disc access time are all essential.

Difference Between Rotational Latency And Disk Assess Time In Disk Scheduling

The time it takes for the read/write head of a hard drive to detect the physical position of a piece of data on the disk is known as seek time. After a complete search, the average time it takes for the sector to move to the next location is called latency.

Rotational Latency

The disc is split into several circular tracks, which are further subdivided into chunks called sectors. The read-write head is moved by the actuator arm to a specific track above the plate as the platter rotates to place the specified sector under the read-write head. Rotational latency is the time it takes to rotate the platter and keep the data under the read-write header. This delay is measured in milliseconds and is determined by the rotational speed of the spindle. The average rotational delay of a disc is half of the time it takes for the disc to complete one revolution. This delay is measured in milliseconds and is determined by the rotational speed of the spindle. The average rotational delay of a disc is half of the time it takes for the disc to complete one revolution.

The rotating speed of a disc or spindle motor, measured in revolutions per minute, determines the rotational latency time (RPM). The average rotational latency for most magnetic media-based drives is usually based on the empirical relation that the average delay in milliseconds for such drives is half of the rotational period. The two types of disc rotation techniques are as follows:

  • Constant linear velocity (CLV), used mostly in optical storage, varies the rotational speed of the optical disc depending on the position of the he
  • Constant angular velocity (CAV), used in most HDDs, standard FDD, some optical disc systems and vinyl audio records, rotates the media at a constant speed, regardless of where the head is locate

Disk Access Time

The overall time taken by the computer to perform a read/write request and then obtain the relevant data from disc storage is known as disc access time. Disk access time is divided into two halves. The first factor is search time, which is the time it takes for the read and write arm to locate the required track. Latency, or wait time, is the time it takes for the head write arm to wait for the required sector on the track to rotate around. The time it takes to access data on drives is measured in milliseconds. This is, however, far slower than CPU processing rates. Although I/O is still sluggish, it cannot keep up with the advances in CPU performance. There are two elements to the disc access time:

  • Data Transfer Time
  • Access Time

Access Time

The preparation time before the actual data transfer is represented as the access time. For example, the read/write head is on track 1, but we need to read data from a different track or segment. As a result, before the actual transfer, the read/write head will relocate to the data block position. This lag is referred to as Access Time. The following factors are added together to determine access time:

Seek Time

The time it takes the read/write head to reach the intended output is called seek time. It is recognized as the most crucial period since it cannot be missed. The amount of time it takes to find something is inversely related to the amount of time it takes to find it. The better the performance, the shorter the seek time.

Main Difference

S no.

Rotational Latency

Disk Access


Rotational Latency = Intersection of the present and necessary sectors / Rotational frequency.

Disk Access =Time spent seeking + rotational latency + time spent transferring data.


Because the exact physical position of blocks is not accessible in most current systems, most disc scheduling does not include rotational frequency.

In comparison to Seek time, it is rather enormous.


The spindle's rotating speed determines rotational latency.

The two components of disk access time are access time and data transfer time.


If a later request comes from a neighbouring sector, rotational latency can be minimised.

If we can reduce the access time and data transfer time, we can reduce the disk access time.