Q 74,paper 3,j12. On a disk with 1000 cylinders (0 to 999) find the number of tracks,the disk arm must move to satisfy all the requests in the disk queue. Assume the last request service was at track 345 and the head is moving oward track 0. The queue in FIFO order contains requests for the following tracks : 123, 874, 692, 475, 105, 376 (Assume SCAN algorithm)
(A) 2013
(B) 1219
(C) 1967
(D) 1507
Answer(B).
Scan algorithm is elevator scan first it will
go in one of the direction then it will reverse to other direction.
Last service was at 345 and it was going
towards the beginning.
(345-123)+(123-105)+(105-0)+(0-376)+(376-475)+(475-692)+(692-874).
=1219.
This is a bit unclear to me. The last service in question is given as 345 so it should come to 345 from 875 (last one). But in the solution, it is started from 345 only.please explain.
ReplyDeleteThis is quite unclear....my answer is 529 and your answer is 1219...how it is possible please explain me
ReplyDeleteYes this is not fair. How come you got
ReplyDelete