1.FCFS
Is the simplest of all the Disk Scheduling Algorithms. In FCFS, the requests are addressed in the order they arrive in the disk queue.
2.SSTF
It seems reasonable to service all the requests close to the current head position before moving the head far away to service other request .This assumption is the basis for the shortest-seek-time-first(SSTF) algorithm. The SSTF algorithm selects the request with the minimum seek time from the current head position Since seek time increases with the number fo cylinders traversed by the head SSTF chooses the pending request closest to the current head position.
3.
In the SCAN algorithm, the disk arm starts at one end of the disk and moves toward the other end, servicing requests as it reaches each cylinder, until it gets to the other end of the disk.
4.
SCAN algorithm, the disk arm again scans the path that has been scanned, after reversing its direction. So, it may be possible that too many requests are waiting at the other end or there may be zero or few requests pending at the scanned area.These situations are avoided in
CSCAN algorithm in which the disk arm instead of reversing its direction goes to the other end of the disk and starts servicing the requests from there. So, the disk arm moves in a circular fashion and this algorithm is also similar to SCAN algorithm and hence it is known as C-SCAN (Circular SCAN).
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