itec 502 컴퓨터 시스템 및 실습 chapter 9-1: disk scheduling mi-jung choi...
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ITEC 502 컴퓨터 시스템 및 실습
Chapter 9-1:Disk Scheduling
Mi-Jung Choimjchoi@postech.ac.kr
DPNM Lab. Dept. of CSE, POSTECH
ITEC502 컴퓨터 시스템 및 실습
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Contents
Disk Hardware Disk Formatting Disk Arm Scheduling Algorithms
ITEC502 컴퓨터 시스템 및 실습
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Moving-head Disk Machanism
ITEC502 컴퓨터 시스템 및 실습
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DisksDisk Hardware (1)
Disk parameters for the original IBM PC floppy disk and a Western Digital WD 18300 hard disk
ITEC502 컴퓨터 시스템 및 실습
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Disk Hardware (2)
Physical geometry of a disk with two zones A possible virtual geometry for this disk
ITEC502 컴퓨터 시스템 및 실습
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Disk Hardware (3)
Raid levels 0 through 2 Backup and parity drives are shaded
ITEC502 컴퓨터 시스템 및 실습
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Disk Hardware (4)
Raid levels 3 through 5 Backup and parity drives are shaded
ITEC502 컴퓨터 시스템 및 실습
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Disk Hardware (5)
Recording structure of a CD or CD-ROM
ITEC502 컴퓨터 시스템 및 실습
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Disk Hardware (6)
Logical data layout on a CD-ROM
ITEC502 컴퓨터 시스템 및 실습
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Disk Hardware (7)
Cross section of a CD-R disk and laser– not to scale
Silver CD-ROM has similar structure– without dye layer– with pitted aluminum layer instead of gold
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Disk Hardware (8)
A double sided, dual layer DVD disk
ITEC502 컴퓨터 시스템 및 실습
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Disk Formatting (1)
A disk sector
ITEC502 컴퓨터 시스템 및 실습
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Disk Formatting (2)
An illustration of cylinder skew
ITEC502 컴퓨터 시스템 및 실습
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Disk Formatting (3)
No interleaving Single interleaving Double interleaving
ITEC502 컴퓨터 시스템 및 실습
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Disk Arm Scheduling Algorithms (1)
Time required to read or write a disk block determined by 3 factors
1. Seek time2. Rotational delay3. Actual transfer time
Seek time dominates Error checking is done by
controllers
ITEC502 컴퓨터 시스템 및 실습
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Disk Arm Scheduling Algorithms (2)
Shortest Seek First (SSF) disk scheduling algorithm
Initialposition
Pendingrequests
ITEC502 컴퓨터 시스템 및 실습
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Disk Arm Scheduling Algorithms (3)
The elevator algorithm for scheduling disk requests
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