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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

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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

Difference between SSTF and LOOK Disk Scheduling Algorithm

Shortest Seek Time First / SSTF

Shortest Seek Time First (SSTF) is an acronym for "shortest seek time first." The task request that is closest to the present position of the head or pointer is served by this algorithm. The direction of the head is crucial in estimating total head movement in this case. If there is a tie between requests, the request that confronts it in its current direction will be served by the head. The SSTF algorithm, unlike C-LOOK, is particularly efficient in terms of overall search time. Requests with least time demand are first processed in SSTF. As a result, every request's seek time is computed ahead of time in the queue, and requests are scheduled according to their predicted seek time. As a result, the request that is closest to the disc arm will be processed first. SSTF is a significant improvement over FCFS, since it reduces average response time and enhances system throughput.

It's a suitable batch processing system solution. It does not always assure justice because hunger is a possibility with this schedule. This policy is often unsuitable for interactive systems, as it leads to greater response time fluctuations.


  • When compared to FCFS, it decreases overall seek time.
  • It has a higher throughput and has a shorter average response time and waiting time.


  • There is a cost associated with locating the most recent request.
  • And queries that aren't close to the head may run out of CPU resources.
  • It offers a wide range of response and waiting times.
  • The algorithm is slowed by often changing the orientation of the head.

LOOK Disc Scheduling Algorithm

The LOOK algorithm is a better version of the SCAN algorithm. The head begins serving the first request on one side of the disc and advances to the opposite end of the disc, fulfilling all requests in between. Unlike SCAN, the head goes to the last request instead of the final track, and then the direction is adjusted. It does not, unlike SSTF, serve the task request that is closest to the current head or pointer location. It's identical to the SCAN disc scheduling method, except that instead of travelling to the end of the disc, the disc arm only goes to the last request to be handled in front of the head and then reverses course from there. As a result, the additional time caused by unneeded traversal to the disk's end is avoided.


  • When there are no requests to be served, it does not force the head to move until the end of the disc.
  • When compared to the SCAN Algorithm, it performs better.
  • It does not result in hunger.
  • It has a low reaction time and waiting time variance.


  • There is a cost associated with locating the final requests.
  • It also results in a significant delay for the cylinders that the head has just visited.

Main Difference

1.SCAN Even if there are no requests at the ends, the algorithm scans all of the cylinders on the drive from one end to the other.  Starting with the initial request at one end and ending with the final request at the other, the LOOK Algorithm examines all of the cylinders on the disc.  
2.The performance of the SSTF disc scheduling method is slow.The LOOK disc scheduling technique outperforms SSTF in terms of performance.
3.When compared to the LOOK disc scheduling technique, it decreases overall seek time.The overall seek time has been raised by the LOOK disc scheduling technique.
4.The average response time and waiting time for this method have both high variation.It has a low standard deviation in average waiting and response times.
5.The orientation of the head, as indicated in the picture above, is critical in breaking the tie between requests.When the LOOK disc scheduling algorithm fulfils the final request in one direction, the head's orientation is reversed.
6.There is a cost to identifying the nearest request in the SSTF disc scheduling method.There is a cost to locating end requests in this method.
7.The request that is distant from the head will be starved in the SSTF disc scheduling mechanism.The request that is far from the top of the queue will be starved. Any request is not starved by the LOOK disc scheduling mechanism.
8.Request handling is not as excellent in the SSTF disc scheduling method as it is in the LOOK algorithm.The LOOK disc scheduling technique is more efficient than SSTF at handling requests.