disk scheduling

Question

In disk scheduling if header movement direction is not given then which way to move? Please provide any link or source in support of your answer. Thanks

Comments

according to algo which we use like FCFS , SSTF,SCAN,C-SCAN,LOOK,C-LOOK

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If. Scan is applied which direction will header go if not mentioned in question??

Answer 1

@kamakshi

suppose track request are 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

SCAN (ELEVATOR):

This approach works like an elevator does. 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. This process moved a total of 230 tracks. Once again this is more optimal than the previous algorithm, but it is not the best.

if Direction is given follow it otherwise go to nearest end.

Comments

If the distance of head is same from both ends then which direction will it go. For example header is currently at 50 and cylinder are varying from 0to 100 then from both sides the distance is 50. In this case where the head will start it's move?

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@kamakshi  i think try both side which is available in options you can go with that only

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Can u please provide any source in support of ur answer?

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@ kamakshi plz check this