SlideShare a Scribd company logo
Disk
Management
Disk Management
Disk formatting
–Low-level formatting, or physical formatting
–Dividing a disk into sectors that the disk
controller can read and write.
• Boot Block
• Bad Block
Disk Formatting
• Low-level formatting, or physical
formatting
• Divide a disk into sectors that the
controller can read and write
–A new disk is a blank state –Fill each
sector with a special data structure:
header –data –trailer
Disk Formatting (con..)
• Header and Trailer contains information used by
disk controller
–A sector number and an error-correcting
code (ECC)
• When the controller writes a sector of data
–ECC is updated with a value calculated from
all the bytes in the data area
• When the sector is read, ECC is recalculated
and is compared with the stored value  verify
the data is correct
Disk Partition
• To use a disk to hold files, OS still needs
to record its own data structures on the
disk
• Partition the disk into one or more groups
of cylinders
–Each partition can be treated as a
separate disk
Disk Partition (con..)
• Logical formatting or “making a file
system”
–Store the initial file-system data
structure onto the disk…
• Maps of free and allocated space (FAT or
innode)
• An initial empty directory NCHU System &
Network Lab
Raw Disk
• Use a disk partition as a large sequential
array of logical blocks
–Without any file-system data
structures
• This array is called raw disk
–The I/Os to the array is called raw I/O
Example –swap space
Raw Disk (con..)
• Raw I/O bypasses all the file-system
services
–Such as the buffer cache, file locking,
pre-fetching, space allocation, file names,
and directories
Boot Block
• Bootstrap program initializes system. –
Initialize CPU registers, device controllers,
main memory –Start OS
• In PC, two-step approaches
–A tiny bootstrap program is stored in
ROM.
• Bring in a full bootstrap program from
disk, a bootstrap loader
Boot Block (con..)
–Full bootstrap program.
• Stored in boot block: at a fixed location on
the disk
• Load the OS and start the OS
• This disk is called boot disk or system disk
Bad Blocks
• IDE –MS-DOS format : performs logical
formatting
• Scan the disk to find bad blocks
• Write a special value into the
corresponding FAT entry for bad blocks
–MS-DOS chkdsk : if blocks go bad
during operations •Search and lock bad
blocks
Bad Blocks (Cont.)
• SCSI –Controller maintains a list of bad
blocks on the disk
–Low-level formatting will set aside
spare sectors
• OS don’t know –Sector sparing (or
forwarding):
•Controller replaces each bad sector
logically with one of the spare sectors
Bad Blocks (Cont.)
• Invalidate optimization by OS’s disk
scheduling
–Sol: Each cylinder has a few spare
sectors
• Another technique: sector slipping
–Ex. 17 defective, spare follows sector
202 •Spare  202  201  … 18  17
Booting from a Disk in
Windows 2000

More Related Content

Similar to diskmanagement-170307012154.pdf

Windows Forensics- Introduction and Analysis
Windows Forensics- Introduction and AnalysisWindows Forensics- Introduction and Analysis
Windows Forensics- Introduction and Analysis
Don Caeiro
 
Disk
DiskDisk
Computer details
Computer detailsComputer details
Computer details
Krishna Yadav Kyadav308
 
Module5 secondary storage
Module5 secondary storageModule5 secondary storage
Module5 secondary storage
ChethanaThammaiah
 
Laptop Basic Knowledge
Laptop Basic KnowledgeLaptop Basic Knowledge
Laptop Basic Knowledge
VIRENDRA SHARMA
 
Computer Main Comppponents.pdf
Computer Main Comppponents.pdfComputer Main Comppponents.pdf
Computer Main Comppponents.pdf
thinalost
 
File system performance
File system performanceFile system performance
File system performance
Vijay Yadav
 
Magnetism data addressing
Magnetism data addressingMagnetism data addressing
Magnetism data addressing
Pooja Shukla
 
Introduction to filesystems and computer forensics
Introduction to filesystems and computer forensicsIntroduction to filesystems and computer forensics
Introduction to filesystems and computer forensics
Mayank Chaudhari
 
BSP.pptx
BSP.pptxBSP.pptx
BSP.pptx
taruian
 
Os
OsOs
Thiru
ThiruThiru
Mass storage systemsos
Mass storage systemsosMass storage systemsos
Mass storage systemsos
Gokila Manickam
 
9781111306366 ppt ch4
9781111306366 ppt ch49781111306366 ppt ch4
9781111306366 ppt ch4
Dr. Ahmed Al Zaidy
 
Operating Systems
Operating SystemsOperating Systems
Operating Systems
Geetha Kannan
 
Ugif 10 2012 beauty ofifmxdiskstructs ugif
Ugif 10 2012 beauty ofifmxdiskstructs ugifUgif 10 2012 beauty ofifmxdiskstructs ugif
Ugif 10 2012 beauty ofifmxdiskstructs ugifUGIF
 
Asif Jamal disk (it)
Asif Jamal disk (it)Asif Jamal disk (it)
Asif Jamal disk (it)Asif Jamal
 
OS Unit5.pptx
OS Unit5.pptxOS Unit5.pptx
OS Unit5.pptx
DHANABALSUBRAMANIAN
 
Os
OsOs

Similar to diskmanagement-170307012154.pdf (20)

Windows Forensics- Introduction and Analysis
Windows Forensics- Introduction and AnalysisWindows Forensics- Introduction and Analysis
Windows Forensics- Introduction and Analysis
 
Disk
DiskDisk
Disk
 
Computer details
Computer detailsComputer details
Computer details
 
Module5 secondary storage
Module5 secondary storageModule5 secondary storage
Module5 secondary storage
 
Laptop Basic Knowledge
Laptop Basic KnowledgeLaptop Basic Knowledge
Laptop Basic Knowledge
 
Computer Main Comppponents.pdf
Computer Main Comppponents.pdfComputer Main Comppponents.pdf
Computer Main Comppponents.pdf
 
File system performance
File system performanceFile system performance
File system performance
 
Magnetism data addressing
Magnetism data addressingMagnetism data addressing
Magnetism data addressing
 
Disk formatting
Disk formattingDisk formatting
Disk formatting
 
Introduction to filesystems and computer forensics
Introduction to filesystems and computer forensicsIntroduction to filesystems and computer forensics
Introduction to filesystems and computer forensics
 
BSP.pptx
BSP.pptxBSP.pptx
BSP.pptx
 
Os
OsOs
Os
 
Thiru
ThiruThiru
Thiru
 
Mass storage systemsos
Mass storage systemsosMass storage systemsos
Mass storage systemsos
 
9781111306366 ppt ch4
9781111306366 ppt ch49781111306366 ppt ch4
9781111306366 ppt ch4
 
Operating Systems
Operating SystemsOperating Systems
Operating Systems
 
Ugif 10 2012 beauty ofifmxdiskstructs ugif
Ugif 10 2012 beauty ofifmxdiskstructs ugifUgif 10 2012 beauty ofifmxdiskstructs ugif
Ugif 10 2012 beauty ofifmxdiskstructs ugif
 
Asif Jamal disk (it)
Asif Jamal disk (it)Asif Jamal disk (it)
Asif Jamal disk (it)
 
OS Unit5.pptx
OS Unit5.pptxOS Unit5.pptx
OS Unit5.pptx
 
Os
OsOs
Os
 

More from BhanuCharan9

SOCIAL DISTANCE DETECTION.pptx
SOCIAL DISTANCE DETECTION.pptxSOCIAL DISTANCE DETECTION.pptx
SOCIAL DISTANCE DETECTION.pptx
BhanuCharan9
 
BLOCKHUNTER.pptx
BLOCKHUNTER.pptxBLOCKHUNTER.pptx
BLOCKHUNTER.pptx
BhanuCharan9
 
productionanalysis-090913125852-phpapp01.pdf
productionanalysis-090913125852-phpapp01.pdfproductionanalysis-090913125852-phpapp01.pdf
productionanalysis-090913125852-phpapp01.pdf
BhanuCharan9
 
marketstructurereview-121123101318-phpapp02.pdf
marketstructurereview-121123101318-phpapp02.pdfmarketstructurereview-121123101318-phpapp02.pdf
marketstructurereview-121123101318-phpapp02.pdf
BhanuCharan9
 
unit1rulesofinference-170113152312.pdf
unit1rulesofinference-170113152312.pdfunit1rulesofinference-170113152312.pdf
unit1rulesofinference-170113152312.pdf
BhanuCharan9
 
mathematicalinductionanddivisibilityrules-160711105713.pdf
mathematicalinductionanddivisibilityrules-160711105713.pdfmathematicalinductionanddivisibilityrules-160711105713.pdf
mathematicalinductionanddivisibilityrules-160711105713.pdf
BhanuCharan9
 
0th-review-1.pptx
0th-review-1.pptx0th-review-1.pptx
0th-review-1.pptx
BhanuCharan9
 
Blockchain Banking 0th Review.pptx
Blockchain Banking 0th Review.pptxBlockchain Banking 0th Review.pptx
Blockchain Banking 0th Review.pptx
BhanuCharan9
 
timesproet-180212053847.pdf
timesproet-180212053847.pdftimesproet-180212053847.pdf
timesproet-180212053847.pdf
BhanuCharan9
 
slide5keys-140722233859-phpapp02.pdf
slide5keys-140722233859-phpapp02.pdfslide5keys-140722233859-phpapp02.pdf
slide5keys-140722233859-phpapp02.pdf
BhanuCharan9
 
neerajppt-130323071407-phpapp02.pdf
neerajppt-130323071407-phpapp02.pdfneerajppt-130323071407-phpapp02.pdf
neerajppt-130323071407-phpapp02.pdf
BhanuCharan9
 
criticalsectionproblem-160905215747.pdf
criticalsectionproblem-160905215747.pdfcriticalsectionproblem-160905215747.pdf
criticalsectionproblem-160905215747.pdf
BhanuCharan9
 
analysisofsupply-160417044322.pdf
analysisofsupply-160417044322.pdfanalysisofsupply-160417044322.pdf
analysisofsupply-160417044322.pdf
BhanuCharan9
 
relationsandfunctionslessonproper-160929053921.pdf
relationsandfunctionslessonproper-160929053921.pdfrelationsandfunctionslessonproper-160929053921.pdf
relationsandfunctionslessonproper-160929053921.pdf
BhanuCharan9
 
coloring.pptx
coloring.pptxcoloring.pptx
coloring.pptx
BhanuCharan9
 
coloring.ppt
coloring.pptcoloring.ppt
coloring.ppt
BhanuCharan9
 

More from BhanuCharan9 (16)

SOCIAL DISTANCE DETECTION.pptx
SOCIAL DISTANCE DETECTION.pptxSOCIAL DISTANCE DETECTION.pptx
SOCIAL DISTANCE DETECTION.pptx
 
BLOCKHUNTER.pptx
BLOCKHUNTER.pptxBLOCKHUNTER.pptx
BLOCKHUNTER.pptx
 
productionanalysis-090913125852-phpapp01.pdf
productionanalysis-090913125852-phpapp01.pdfproductionanalysis-090913125852-phpapp01.pdf
productionanalysis-090913125852-phpapp01.pdf
 
marketstructurereview-121123101318-phpapp02.pdf
marketstructurereview-121123101318-phpapp02.pdfmarketstructurereview-121123101318-phpapp02.pdf
marketstructurereview-121123101318-phpapp02.pdf
 
unit1rulesofinference-170113152312.pdf
unit1rulesofinference-170113152312.pdfunit1rulesofinference-170113152312.pdf
unit1rulesofinference-170113152312.pdf
 
mathematicalinductionanddivisibilityrules-160711105713.pdf
mathematicalinductionanddivisibilityrules-160711105713.pdfmathematicalinductionanddivisibilityrules-160711105713.pdf
mathematicalinductionanddivisibilityrules-160711105713.pdf
 
0th-review-1.pptx
0th-review-1.pptx0th-review-1.pptx
0th-review-1.pptx
 
Blockchain Banking 0th Review.pptx
Blockchain Banking 0th Review.pptxBlockchain Banking 0th Review.pptx
Blockchain Banking 0th Review.pptx
 
timesproet-180212053847.pdf
timesproet-180212053847.pdftimesproet-180212053847.pdf
timesproet-180212053847.pdf
 
slide5keys-140722233859-phpapp02.pdf
slide5keys-140722233859-phpapp02.pdfslide5keys-140722233859-phpapp02.pdf
slide5keys-140722233859-phpapp02.pdf
 
neerajppt-130323071407-phpapp02.pdf
neerajppt-130323071407-phpapp02.pdfneerajppt-130323071407-phpapp02.pdf
neerajppt-130323071407-phpapp02.pdf
 
criticalsectionproblem-160905215747.pdf
criticalsectionproblem-160905215747.pdfcriticalsectionproblem-160905215747.pdf
criticalsectionproblem-160905215747.pdf
 
analysisofsupply-160417044322.pdf
analysisofsupply-160417044322.pdfanalysisofsupply-160417044322.pdf
analysisofsupply-160417044322.pdf
 
relationsandfunctionslessonproper-160929053921.pdf
relationsandfunctionslessonproper-160929053921.pdfrelationsandfunctionslessonproper-160929053921.pdf
relationsandfunctionslessonproper-160929053921.pdf
 
coloring.pptx
coloring.pptxcoloring.pptx
coloring.pptx
 
coloring.ppt
coloring.pptcoloring.ppt
coloring.ppt
 

Recently uploaded

Guidance_and_Counselling.pdf B.Ed. 4th Semester
Guidance_and_Counselling.pdf B.Ed. 4th SemesterGuidance_and_Counselling.pdf B.Ed. 4th Semester
Guidance_and_Counselling.pdf B.Ed. 4th Semester
Atul Kumar Singh
 
Polish students' mobility in the Czech Republic
Polish students' mobility in the Czech RepublicPolish students' mobility in the Czech Republic
Polish students' mobility in the Czech Republic
Anna Sz.
 
Adversarial Attention Modeling for Multi-dimensional Emotion Regression.pdf
Adversarial Attention Modeling for Multi-dimensional Emotion Regression.pdfAdversarial Attention Modeling for Multi-dimensional Emotion Regression.pdf
Adversarial Attention Modeling for Multi-dimensional Emotion Regression.pdf
Po-Chuan Chen
 
Biological Screening of Herbal Drugs in detailed.
Biological Screening of Herbal Drugs in detailed.Biological Screening of Herbal Drugs in detailed.
Biological Screening of Herbal Drugs in detailed.
Ashokrao Mane college of Pharmacy Peth-Vadgaon
 
2024.06.01 Introducing a competency framework for languag learning materials ...
2024.06.01 Introducing a competency framework for languag learning materials ...2024.06.01 Introducing a competency framework for languag learning materials ...
2024.06.01 Introducing a competency framework for languag learning materials ...
Sandy Millin
 
Chapter 3 - Islamic Banking Products and Services.pptx
Chapter 3 - Islamic Banking Products and Services.pptxChapter 3 - Islamic Banking Products and Services.pptx
Chapter 3 - Islamic Banking Products and Services.pptx
Mohd Adib Abd Muin, Senior Lecturer at Universiti Utara Malaysia
 
Language Across the Curriculm LAC B.Ed.
Language Across the  Curriculm LAC B.Ed.Language Across the  Curriculm LAC B.Ed.
Language Across the Curriculm LAC B.Ed.
Atul Kumar Singh
 
CLASS 11 CBSE B.St Project AIDS TO TRADE - INSURANCE
CLASS 11 CBSE B.St Project AIDS TO TRADE - INSURANCECLASS 11 CBSE B.St Project AIDS TO TRADE - INSURANCE
CLASS 11 CBSE B.St Project AIDS TO TRADE - INSURANCE
BhavyaRajput3
 
Sha'Carri Richardson Presentation 202345
Sha'Carri Richardson Presentation 202345Sha'Carri Richardson Presentation 202345
Sha'Carri Richardson Presentation 202345
beazzy04
 
The Accursed House by Émile Gaboriau.pptx
The Accursed House by Émile Gaboriau.pptxThe Accursed House by Émile Gaboriau.pptx
The Accursed House by Émile Gaboriau.pptx
DhatriParmar
 
The Roman Empire A Historical Colossus.pdf
The Roman Empire A Historical Colossus.pdfThe Roman Empire A Historical Colossus.pdf
The Roman Empire A Historical Colossus.pdf
kaushalkr1407
 
Digital Tools and AI for Teaching Learning and Research
Digital Tools and AI for Teaching Learning and ResearchDigital Tools and AI for Teaching Learning and Research
Digital Tools and AI for Teaching Learning and Research
Vikramjit Singh
 
CACJapan - GROUP Presentation 1- Wk 4.pdf
CACJapan - GROUP Presentation 1- Wk 4.pdfCACJapan - GROUP Presentation 1- Wk 4.pdf
CACJapan - GROUP Presentation 1- Wk 4.pdf
camakaiclarkmusic
 
special B.ed 2nd year old paper_20240531.pdf
special B.ed 2nd year old paper_20240531.pdfspecial B.ed 2nd year old paper_20240531.pdf
special B.ed 2nd year old paper_20240531.pdf
Special education needs
 
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...
Levi Shapiro
 
The French Revolution Class 9 Study Material pdf free download
The French Revolution Class 9 Study Material pdf free downloadThe French Revolution Class 9 Study Material pdf free download
The French Revolution Class 9 Study Material pdf free download
Vivekanand Anglo Vedic Academy
 
Phrasal Verbs.XXXXXXXXXXXXXXXXXXXXXXXXXX
Phrasal Verbs.XXXXXXXXXXXXXXXXXXXXXXXXXXPhrasal Verbs.XXXXXXXXXXXXXXXXXXXXXXXXXX
Phrasal Verbs.XXXXXXXXXXXXXXXXXXXXXXXXXX
MIRIAMSALINAS13
 
Overview on Edible Vaccine: Pros & Cons with Mechanism
Overview on Edible Vaccine: Pros & Cons with MechanismOverview on Edible Vaccine: Pros & Cons with Mechanism
Overview on Edible Vaccine: Pros & Cons with Mechanism
DeeptiGupta154
 
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
siemaillard
 
"Protectable subject matters, Protection in biotechnology, Protection of othe...
"Protectable subject matters, Protection in biotechnology, Protection of othe..."Protectable subject matters, Protection in biotechnology, Protection of othe...
"Protectable subject matters, Protection in biotechnology, Protection of othe...
SACHIN R KONDAGURI
 

Recently uploaded (20)

Guidance_and_Counselling.pdf B.Ed. 4th Semester
Guidance_and_Counselling.pdf B.Ed. 4th SemesterGuidance_and_Counselling.pdf B.Ed. 4th Semester
Guidance_and_Counselling.pdf B.Ed. 4th Semester
 
Polish students' mobility in the Czech Republic
Polish students' mobility in the Czech RepublicPolish students' mobility in the Czech Republic
Polish students' mobility in the Czech Republic
 
Adversarial Attention Modeling for Multi-dimensional Emotion Regression.pdf
Adversarial Attention Modeling for Multi-dimensional Emotion Regression.pdfAdversarial Attention Modeling for Multi-dimensional Emotion Regression.pdf
Adversarial Attention Modeling for Multi-dimensional Emotion Regression.pdf
 
Biological Screening of Herbal Drugs in detailed.
Biological Screening of Herbal Drugs in detailed.Biological Screening of Herbal Drugs in detailed.
Biological Screening of Herbal Drugs in detailed.
 
2024.06.01 Introducing a competency framework for languag learning materials ...
2024.06.01 Introducing a competency framework for languag learning materials ...2024.06.01 Introducing a competency framework for languag learning materials ...
2024.06.01 Introducing a competency framework for languag learning materials ...
 
Chapter 3 - Islamic Banking Products and Services.pptx
Chapter 3 - Islamic Banking Products and Services.pptxChapter 3 - Islamic Banking Products and Services.pptx
Chapter 3 - Islamic Banking Products and Services.pptx
 
Language Across the Curriculm LAC B.Ed.
Language Across the  Curriculm LAC B.Ed.Language Across the  Curriculm LAC B.Ed.
Language Across the Curriculm LAC B.Ed.
 
CLASS 11 CBSE B.St Project AIDS TO TRADE - INSURANCE
CLASS 11 CBSE B.St Project AIDS TO TRADE - INSURANCECLASS 11 CBSE B.St Project AIDS TO TRADE - INSURANCE
CLASS 11 CBSE B.St Project AIDS TO TRADE - INSURANCE
 
Sha'Carri Richardson Presentation 202345
Sha'Carri Richardson Presentation 202345Sha'Carri Richardson Presentation 202345
Sha'Carri Richardson Presentation 202345
 
The Accursed House by Émile Gaboriau.pptx
The Accursed House by Émile Gaboriau.pptxThe Accursed House by Émile Gaboriau.pptx
The Accursed House by Émile Gaboriau.pptx
 
The Roman Empire A Historical Colossus.pdf
The Roman Empire A Historical Colossus.pdfThe Roman Empire A Historical Colossus.pdf
The Roman Empire A Historical Colossus.pdf
 
Digital Tools and AI for Teaching Learning and Research
Digital Tools and AI for Teaching Learning and ResearchDigital Tools and AI for Teaching Learning and Research
Digital Tools and AI for Teaching Learning and Research
 
CACJapan - GROUP Presentation 1- Wk 4.pdf
CACJapan - GROUP Presentation 1- Wk 4.pdfCACJapan - GROUP Presentation 1- Wk 4.pdf
CACJapan - GROUP Presentation 1- Wk 4.pdf
 
special B.ed 2nd year old paper_20240531.pdf
special B.ed 2nd year old paper_20240531.pdfspecial B.ed 2nd year old paper_20240531.pdf
special B.ed 2nd year old paper_20240531.pdf
 
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...
 
The French Revolution Class 9 Study Material pdf free download
The French Revolution Class 9 Study Material pdf free downloadThe French Revolution Class 9 Study Material pdf free download
The French Revolution Class 9 Study Material pdf free download
 
Phrasal Verbs.XXXXXXXXXXXXXXXXXXXXXXXXXX
Phrasal Verbs.XXXXXXXXXXXXXXXXXXXXXXXXXXPhrasal Verbs.XXXXXXXXXXXXXXXXXXXXXXXXXX
Phrasal Verbs.XXXXXXXXXXXXXXXXXXXXXXXXXX
 
Overview on Edible Vaccine: Pros & Cons with Mechanism
Overview on Edible Vaccine: Pros & Cons with MechanismOverview on Edible Vaccine: Pros & Cons with Mechanism
Overview on Edible Vaccine: Pros & Cons with Mechanism
 
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
 
"Protectable subject matters, Protection in biotechnology, Protection of othe...
"Protectable subject matters, Protection in biotechnology, Protection of othe..."Protectable subject matters, Protection in biotechnology, Protection of othe...
"Protectable subject matters, Protection in biotechnology, Protection of othe...
 

diskmanagement-170307012154.pdf

  • 2. Disk Management Disk formatting –Low-level formatting, or physical formatting –Dividing a disk into sectors that the disk controller can read and write. • Boot Block • Bad Block
  • 3. Disk Formatting • Low-level formatting, or physical formatting • Divide a disk into sectors that the controller can read and write –A new disk is a blank state –Fill each sector with a special data structure: header –data –trailer
  • 4. Disk Formatting (con..) • Header and Trailer contains information used by disk controller –A sector number and an error-correcting code (ECC) • When the controller writes a sector of data –ECC is updated with a value calculated from all the bytes in the data area • When the sector is read, ECC is recalculated and is compared with the stored value  verify the data is correct
  • 5. Disk Partition • To use a disk to hold files, OS still needs to record its own data structures on the disk • Partition the disk into one or more groups of cylinders –Each partition can be treated as a separate disk
  • 6. Disk Partition (con..) • Logical formatting or “making a file system” –Store the initial file-system data structure onto the disk… • Maps of free and allocated space (FAT or innode) • An initial empty directory NCHU System & Network Lab
  • 7. Raw Disk • Use a disk partition as a large sequential array of logical blocks –Without any file-system data structures • This array is called raw disk –The I/Os to the array is called raw I/O Example –swap space
  • 8. Raw Disk (con..) • Raw I/O bypasses all the file-system services –Such as the buffer cache, file locking, pre-fetching, space allocation, file names, and directories
  • 9. Boot Block • Bootstrap program initializes system. – Initialize CPU registers, device controllers, main memory –Start OS • In PC, two-step approaches –A tiny bootstrap program is stored in ROM. • Bring in a full bootstrap program from disk, a bootstrap loader
  • 10. Boot Block (con..) –Full bootstrap program. • Stored in boot block: at a fixed location on the disk • Load the OS and start the OS • This disk is called boot disk or system disk
  • 11. Bad Blocks • IDE –MS-DOS format : performs logical formatting • Scan the disk to find bad blocks • Write a special value into the corresponding FAT entry for bad blocks –MS-DOS chkdsk : if blocks go bad during operations •Search and lock bad blocks
  • 12. Bad Blocks (Cont.) • SCSI –Controller maintains a list of bad blocks on the disk –Low-level formatting will set aside spare sectors • OS don’t know –Sector sparing (or forwarding): •Controller replaces each bad sector logically with one of the spare sectors
  • 13. Bad Blocks (Cont.) • Invalidate optimization by OS’s disk scheduling –Sol: Each cylinder has a few spare sectors • Another technique: sector slipping –Ex. 17 defective, spare follows sector 202 •Spare  202  201  … 18  17
  • 14.
  • 15. Booting from a Disk in Windows 2000