What are the common disk scheduling algorithms?

Common disk scheduling algorithms include first come, first served, shortest seek time first, scan algorithm, loop scan algorithm, simple elevator algorithm and loop LOOK algorithm. Detailed introduction: 1. First come, first served, the advantage is that it is simple to implement, but the disadvantage is that it may cause uneven disk access time, causing some requests to wait for too long; 2. The shortest seek time is given priority, and the advantage is that it can improve the disk access efficiency , but the disadvantage is that starvation problems may occur; 3. Scanning algorithm, the advantage is that it can ensure that every request will be satisfied, but the disadvantage is that the waiting time for intermediate requests is too long, etc.

#Disk Scheduling In a multi-programmed computer system, each process may continuously make different requests for read/write operations on the disk. Since sometimes these processes send requests faster than the disk can respond, it is necessary for us to establish a waiting queue for each disk device. Today I have brought you related tutorials and articles. I hope it will be useful to you. helped.

Common disk scheduling algorithms include the following:

1. First-come, first-served (FCFS, First-Come, First-Served): This is the simplest disk scheduling algorithm, disk access is performed in the order of requests. When one request is completed, the next request will be executed. The advantage of this algorithm is that it is simple to implement, but the disadvantage is that it may cause uneven disk access time and cause some requests to wait too long.

2. Shortest seek time first (SSTF, Shortest Seek Time First): This algorithm selects the request closest to the current track for disk access. It will first satisfy the request closest to the current track, thereby reducing seek time. The advantage of this algorithm is that it can improve disk access efficiency, but the disadvantage is that starvation problems may occur, that is, some requests may wait forever and cannot be satisfied.

3. Scanning algorithm (SCAN): This algorithm moves the head in one direction until it reaches the edge, then changes the direction and continues to move, accessing requests in sequence. The advantage of this algorithm is that it can guarantee that every request will be satisfied, but the disadvantage is that intermediate requests may wait for too long.

4. Cyclic Scan Algorithm (C-SCAN): This algorithm is similar to the scanning algorithm. The head moves in one direction until it reaches the edge, and then immediately returns to the other side and continues to move in the same direction. The advantage of this algorithm is that it can reduce the waiting time of intermediate requests, but the disadvantage is that it may cause the outermost and innermost requests to wait too long.

5. Simple elevator algorithm (LOOK): This algorithm moves the head in one direction until it reaches the edge, then returns immediately and continues to move in the opposite direction. The advantage of this algorithm is that it can reduce the waiting time of intermediate requests, but the disadvantage is that it may cause the outermost and innermost requests to wait too long.

6. Cyclic LOOK algorithm (C-LOOK): This algorithm is similar to the LOOK algorithm. The head moves in one direction until it reaches the edge, and then immediately returns to the other side and continues to move in the same direction. The advantage of this algorithm is that it can reduce the waiting time of intermediate requests, but the disadvantage is that it may cause the outermost and innermost requests to wait too long.

These algorithms have their own advantages and disadvantages and are suitable for different disk access scenarios. Choosing an appropriate disk scheduling algorithm can improve disk access efficiency, reduce waiting time, and improve system performance.

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