OS_ch12_F07 - by I.-C. Lin, Dept. CS, NCTU. Textbook:...

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by I.-C. Lin, Dept. CS, NCTU. Textbook: Operating System Principles 7ed CHAPTER 12: SECONDARY- STORAGE SYSTEMS
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hapter 12: Mass- torage Systems Chapter 12: Mass Storage Systems verview of Mass torage Structure ± Overview of Mass-Storage Structure ± Disk Structure ± Disk Attachment ± Disk Scheduling ± Disk Management ± Swap-Space Management ± RAID Structure ± Stable-Storage Implementation ± Tertiary-Storage Structure
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bjectives Objectives i b t h h i l t t f d d t t i t ± Describe the physical structure of secondary and tertiary storage devices and the resulting effects on the uses of the devices ± Explain the performance characteristics of mass-storage devices ± Discuss operating-system services provided for mass storage, cluding including: ± RAID (Redudant Arrays of Inexpensive Disks ) SM (Hierarchical Storage Management) ± HSM (Hierarchical Storage Management) ±
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verview of Mass- torage Structure Overview of Mass Storage Structure agnetic disks provide bulk of secondary storage of modern ± Magnetic disks provide bulk of secondary storage of modern computers rives rotate at 60 to 200 times per second (3600~12000rpm) ± Drives rotate at 60 to 200 times per second (3600 12000rpm) ± Transfer rate ² the rate at which data flow between drive and computer ± Positioning time ( random-access time ) ² time to move the disk arm to desired cylinder ( seek time ) and time for the esired sector to rotate under the disk head ( tational latency desired sector to rotate under the disk head ( rotational latency ) ± Head crash results from disk head making contact with the disk surface
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verview of Mass- torage Structure Overview of Mass Storage Structure isks can be removable ± Disks can be removable ± Drive attached to computer via I/O bus ± Buses vary, including DE(Enhanced tegrated Drive Electronics ² EIDE(Enhanced Integrated Drive Electronics ) ² SATA(Serial Advanced Technology Attachment ) ² USB(Universal Serial Bus) ² SCSI(Small Computer System Interface) ² etc. ± Host controller in computer uses bus to talk to disk controller built into drive or storage array
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oving- ad Disk Mechanism Moving head Disk Mechanism
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verview of Mass Storage Structure (Cont ) Overview of Mass Storage Structure (Cont.) agnetic tape ± Magnetic tape ± Was early secondary-storage medium elatively permanent and holds large quantities of data ± Relatively permanent and holds large quantities of data ± Access time slow ± Random access ~1000 times slower than disk ± Mainly used for backup, storage of infrequently-used data, transfer medium between systems ± Kept in spool and wound or rewound past read-write head ± Once data under head, transfer rates comparable to disk 0 00GB typical storage ± 20-200GB typical storage ± Common technologies are 4mm, 8mm, 19mm, LTO-2 and SDLT
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isk Structure Disk Structure isk drives are addressed as large 1 imensional arrays of ± Disk drives are addressed as large 1-dimensional arrays of logical blocks.
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OS_ch12_F07 - by I.-C. Lin, Dept. CS, NCTU. Textbook:...

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