The disk-scheduling algorithm should be written as a. Requests for disk service can be influenced by the file- allocation method. Performance depends on the number and types of requests. Selecting a Disk-Scheduling Algorithm SSTF is common and has a natural appeal SCAN and C-SCAN perform better for systems that place a heavy load on the disk.
Using this algorithm doesn't provide the best results.The circular SCAN algorithm works in the same way as SCAN except that it always scans in one direction. Whatever number that is next in the queue will be the next number served. SCAN, C-SCAN, LOOK and C-LOOK are high.Given the following queue - 95, 180, 34, 119, 11, 123, 62, 64 with the Read-write head initially at the track 50 and the tail track being at 199 let us now discuss the different algorithms.Abstract This review paper compares the various disk scheduling algorithms that are used to schedule processes in a queue, such as FCFS, SSTF, SCAN, C-SCAN, LOOK, C-LOOK, OTHDSA, and Zone Base Disk Scheduling, and then applies all of these techniques to two data sets to assess the performance of each algorithm.All incoming requests are placed at the end of the queue.
Overhead to calculate seek time in advanceIi. There is a great chance that starvation would take place.The reason for this is if there were a lot of requests close to each other the other requests will never be handled since the distance will always be greater.I. The process would continue until all the process are taken care of.For example the next case would be to move from 62 to 64 instead of 34 since there are only 2 tracks between them and not 18 if it were to go the other way.Although this seems to be a better service being that it moved a total of 236 tracks, this is not an optimal one. Starting at 50, the next shortest distance would be 62 instead of 34 since it is only 12 tracks away from 62 and 16 tracks away from 34. May not provide the best possible serviceIn this case request is serviced according to next shortest distance.
This process moved a total of 230 tracks.Once again this is more optimal than the previous algorithm, but it is not the best. It scans down towards the nearest end and then when it hits the bottom it scans up servicing the requests that it didn't get going down.If a request comes in after it has been scanned it will not be serviced until the process comes back down or moves back up. High variance of response time as SSTF favours only some requestsThis approach works like an elevator does.
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