Disk scheduling algorithms are the algorithms that are used for scheduling a disk. We use disk scheduling to schedule the Input/output requests that arrive for the disk. Disk Scheduling is also called Input/output scheduling.
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.
1. Less traveling head time.
2. Fairness.
3. Throughput must be high.
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.
3. 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.
4. Disk Access Time: - We can define disk access time as: Rotational Latency + Transfer Time + Seek Time
5. 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.