S Edit & Create ve Share1..Suppose that a disk drive has 200 cylinders num-bered 0 to 199. The drive is currently serving arequest at cylinder 95, the queue of pendingrequests, in FIFO order is 98, 181, 37, 120, 14,122, 65, 69.Starting from the current head position, whatis the total distance (in cylinders) that the diskarm moves to satisfy all the pending requestsfor each of the following disk scheduling al-gorithm,(1)SCAN(ii) C-SCAN.

Answered: Suppose that a disk drive has 200…

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Calculate the number of disk tracks traversed using the FCFS algorithms for the series of disk track service requests given as 54,36,21,74,46,35,26,67. At the time the first request arrives in the disk request queue, the read/write head is at track 50, moving toward the outer (lower-numbered)tracks. Draw the graph of the movement. Assume that the disk has 100 tracks from 0 to 99.
Consider a memory of size 8KB (8192 bytes) that allows dynamic, variable sized partitioning among processes and uses a linked list to keep track of free spaces (hereafter referred to as the free list) in the memory at any given time. Assume that there are 6 processes and assume that their memory size requirements (in bytes) are as given below: Р1: 500, Р2: 600, Р3: 1300, Р4: 2000, Р5: 100, Р6: 200 Assume that the initial state of the free list is as shown below (BA is the base address and Sz is the size of each free space): ВА: 0; Sz: 1100 — ВА: 1200; Sz: 600 > BА: 2000; Sz: 1800> ВА: 6000%; Sz 400
Subject: Operating Systems
Suppose that we want to schedule disk requests on a disk containing 200 cylinders numbered from 0 to 199. The Disk requests to be addressed are 82,170,43,140,24,16,189. And the Read/Write arm is at 48, and it is also given that the disk arm should move "towards the larger value". Q₁- Illustrate on a graph the total read/write head movement for the SCAN Disk scheduling algorithm. Q2- Calculate the total overhead movement (total distance covered by the disk arm).
Devise an efficient divide-and-conquer algorithm for the Towers of Hanoi problem when the disks are colored alternately red and blue, and we add the extra rule that no disk may be placed on any other disk of the same color.
Consider a disk subjected to I/O requests arriving (following Poisson distribution) at an average rate of requests/second. Assume that on average, there were 5 requests waiting for service in the queue and that each request waits in the queue for about 10 milliseconds, on average. What is the effective arrival rate for this disk?
Requests are not usually uniformly distributed. For example, a cylinder containing the file system FAT or inodes can be expected to be accessed more frequently than a cylinder that only contains files. Suppose you know that 50 percent of the requests are for a small, fixed number of cylinders. a. Would any of the scheduling algorithms discussed in this chapter be particularly good for this case? Explain your answer. b. Propose a disk-scheduling algorithm that gives even better performance by taking advantage of this "hot spot" on the disk. c. File systems typically find data blocks via an indirection table, such as a FAT in DOS or inodes in UNIX. Describe one or more ways to take advantage of this indirection to improve the disk performance.

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