SCAN vs FCFS in Disk Scheduling Algorithm

Disk scheduling algorithms play a pivotal part in optimizing the execution of disk frameworks by proficiently getting to information. Among the different calculations, Scan (moreover known as the elevator algorithm) and FCFS (First-Come-First-Serve) are two commonly utilized approaches with particular procedures. Check moves the disk arm over the platter in a specific design, adjusting demands because it clears in one course, which minimizes the look for time and improves productivity. On the other hand, FCFS follows a straightforward guideline of servicing the demands within the arrangement they arrive at, without any thought for the area of information on the disk. This article digs into the contrasts between Scan and FCFS, investigating their preferences and impediments in disk planning.

SCAN disk scheduling Algorithm

The Scan disk scheduling algorithm, too known as the elevator algorithm, could be a strategy utilized to get information on a disk productively. It works by moving the disk arm in a specific design over the disk's platter. The arm begins from one conclusion of the disk and moves towards the other conclusion, adjusting all the pending demands in its way.

As the arm moves in a single course, it administrations demand in that heading until it concludes the disk. At that point, it changes its direction and begins overhauling the demands within the inverse course. This back-and-forth development takes after the movement of an elevator traveling up and down a building, thus the title "elevator algorithm."

The Scan algorithm guarantees that all the demands are overhauled, anticipating any uncertain holding up for a specific track. It diminishes the normal look for a time by minimizing the arm's development and expanding the general effectiveness of the disk framework. In any case, it may cause a few delays for demands found at the extraordinary closes of the disk, as they are adjusted as it were when the arm comes to their particular positions

FCFS disk scheduling Algorithm

The FCFS (First-Come-First-Serve) disk scheduling algorithm could be a fundamental approach utilized in overseeing information getting to a disk. In FCFS, the disk arm moves from its current position to the area of the primary ask within the line and performs the necessary perused or type in operation. After completing the current ask, the disk arm moves to the following ask within the line and proceeds with this preparation until all the demands have been handled

One advantage of FCFS is its effortlessness because it requires negligible computational overhead and is simple to execute. Be that as it may, FCFS does not take into consideration the physical area of the information on the disk. Thus, it can result in destitute execution and an expanded look for time if the demands are spread over distinctive areas on the disk.

This need for optimization can lead to longer get-to times and diminished proficiency, particularly in scenarios with an overwhelming workload or tall disk movement. As a result, FCFS is regularly not the foremost efficient choice for disk planning calculations in frameworks that require quicker information recovery or have complex information get to designs.

Differences between SCAN vs FCFS in Disk Scheduling Algorithm

The differences are in the following table −

Basis of Difference




It is additionally known as the elevator algorithm.

FCFS stands for First-Come-First-Serve.


It features a way better throughput than the FCFS planning calculation

It has the most reduced throughput among all disk planning calculations.


It processes requests in one heading until it comes to the disk's conclusion, and after that, the disk arm changes the heading and starts overhauling requests within the inverse arrangement.

It will handle the demands in the way that they arrive within the disk queue.


Average seek time is much lower in comparison to the FCFS planning calculation.

The FCFS planning calculations' normal look for time is the most elevated among all the disk planning calculations which is high


The scan algorithm may happen that the disk arm gets to the request's area, so the ask would take a long holding up time to total.

It includes an arrangement in that demands are handled concurring to plan.


In conclusion, the Scan and FCFS disk scheduling algorithms show differentiating strategies for getting information on a disk. Scan optimizes looking for a time by taking after a particular design, diminishing the normal time required to recover information and improving general effectiveness. On the other hand, FCFS depends exclusively on the arrangement of ask entry, coming about in potential wasteful aspects and expanded look for time if demands are scattered over the disk. When selecting between Scan and FCFS, it is vital to consider the particular prerequisites and characteristics of the framework, such as the workload and information dissemination. Understanding the dissimilarities between these calculations permits educated decision-making to optimize disk execution and information recovery.

Updated on: 18-Jul-2023


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