UGC NET CSE | Junet 2015 | Part 2 | Question: 36

Question

A disk drive has $100$ cylinders, numbered $0$ to $99$. Disk requests come to the disk driver for cylinders $12, 26, 24, 4, 42, 8$ and $50$ in that order. The driver is currently serving a request at a cylinder $24$. A seek takes $6$ msec per cylinder moved. How much seek time is needed for shortest seek time first (SSTF) algorithm?

• A. $0.984$ sec
• B. $0.396$ sec
• C. $0.738$ sec
• D. $0.42$ sec

Answer 1

12, 26, 24, 4, 42, 8 and 50

24-26-12-8-4-42-50 sequence of access

Total (2+14+4+4+38+8) *6ms =( 70*6 /1000 )sec

= 420/1000 = 0.42sec

Answer 2

seek time = 2 =(2 + 14 + 4 + 4 + 38 + 8) = 420 msec
1000 msec = 1 sec
420 msec = 0.42 sec
So, option (D) is correct.