PC Maintenance: PC Maintenance: Preparing for A+ Preparing for A+

CertificationCertificationChapter 10: Introduction to Disk Chapter 10: Introduction to Disk

StorageStorage

Chapter 10 ObjectivesChapter 10 Objectives

Understand magnetic and optical storageUnderstand magnetic and optical storage Explain cylinders, heads, tracks, and Explain cylinders, heads, tracks, and

sectorssectors Understand low-level and high-level Understand low-level and high-level

formattingformatting Explain principles of partitioningExplain principles of partitioning Choose an appropriate file system for the Choose an appropriate file system for the

OS to be installedOS to be installed

How Disks Store DataHow Disks Store Data

Magnetic or opticalMagnetic or optical Based on transitionsBased on transitions

Electrical: positive or negativeElectrical: positive or negative Optical: pit or landOptical: pit or land

Magnetic StorageMagnetic Storage

Hard Disks, Floppy DisksHard Disks, Floppy Disks Polarity change between positive and Polarity change between positive and

negativenegative

Optical StorageOptical Storage

CD, DVDCD, DVD Change between pit (less reflective) and Change between pit (less reflective) and

land (more reflective)land (more reflective)

Disks Versus DrivesDisks Versus Drives

Disk: Platters that store dataDisk: Platters that store data Drive: Mechanism that spins and reads Drive: Mechanism that spins and reads

plattersplatters Hard disk drive: integrated disk and driveHard disk drive: integrated disk and drive Floppy and CD: separate disk and driveFloppy and CD: separate disk and drive

How Disk Space is OrganizedHow Disk Space is Organized

Heads:Heads: Read-write mechanisms, one for Read-write mechanisms, one for each side of each disk plattereach side of each disk platter

How Disk Space is OrganizedHow Disk Space is Organized

Tracks:Tracks: Concentric rings on a platter Concentric rings on a platter

How Disk Space is OrganizedHow Disk Space is Organized

Cylinders:Cylinders: The same track on a stack of The same track on a stack of platters and sidesplatters and sides

How Disk Space is OrganizedHow Disk Space is Organized

Sectors:Sectors: Sections of a track created by Sections of a track created by radial lines from the center of the diskradial lines from the center of the disk

Low-Level FormattingLow-Level Formatting

Creates tracks and sectorsCreates tracks and sectors Defines the disk geometryDefines the disk geometry Done at the factoryDone at the factory

Zoned Recording and Sector Zoned Recording and Sector TranslationTranslation

Zoned Recording:Zoned Recording: Fewer sectors in center Fewer sectors in center of disk than at outer ringsof disk than at outer rings

Sector Translation:Sector Translation: Conversion between Conversion between physical sectors and logical ones needed physical sectors and logical ones needed to interface with PCto interface with PC

Floppy Drive BIOS SupportFloppy Drive BIOS Support

Not Plug and PlayNot Plug and Play

CD-ROM Drive BIOS SupportCD-ROM Drive BIOS Support

Auto (Recommended)Auto (Recommended) CD-ROMCD-ROM

ATAPI RemovableATAPI Removable IDE RemovableIDE Removable

BIOS Translation MethodsBIOS Translation Methods

Standard CHS: Cylinders, Heads, SectorsStandard CHS: Cylinders, Heads, Sectors Extended CHS (ECHS, also called Large)Extended CHS (ECHS, also called Large) Logical Block Addressing LBALogical Block Addressing LBA

Enhanced BIOS Services for Enhanced BIOS Services for Disk DrivesDisk Drives

A BIOS feature, not a drive featureA BIOS feature, not a drive feature Released in 1998Released in 1998 Gives the BIOS the capability to recognize Gives the BIOS the capability to recognize

large drive sizes (over 8.4 GB)large drive sizes (over 8.4 GB) Primary reason why very old PCs cannot Primary reason why very old PCs cannot

see large new drivessee large new drives Requires a BIOS update for motherboard Requires a BIOS update for motherboard

or add-on BIOS utility from drive makeror add-on BIOS utility from drive maker

Data Transfer ModesData Transfer Modes

DMA: Direct Memory AddressingDMA: Direct Memory Addressing Regular and bus masteringRegular and bus mastering

PIO: Programmed Input/Output PIO: Programmed Input/Output PIO modes 0 through 4PIO modes 0 through 4

UltraDMA (Ultra ATA)UltraDMA (Ultra ATA) Modern standard for drive interfacesModern standard for drive interfaces Makes regular DMA and PIO obsoleteMakes regular DMA and PIO obsolete Much faster (33MB/sec to over 150MB/sec)Much faster (33MB/sec to over 150MB/sec)

Disk PartitionsDisk Partitions

Physical drive can be divided upPhysical drive can be divided up Primary partitionPrimary partition Extended partitionExtended partition

Each partition can have one or more Each partition can have one or more logical driveslogical drives Primary partition can have only one drive Primary partition can have only one drive

letterletter Extended partition can have multiple drive Extended partition can have multiple drive

lettersletters

Disk PartitionsDisk Partitions

Active PartitionActive Partition

Bootable partitionBootable partition Only one can be activeOnly one can be active Must be a primary partitionMust be a primary partition

Master Boot RecordMaster Boot Record

Contains information about the physical Contains information about the physical drive’s partitionsdrive’s partitions

Written to the first sector of the first Written to the first sector of the first cylinder of the first headcylinder of the first head

Persists no matter what high-level Persists no matter what high-level formatting is done to the driveformatting is done to the drive

ClustersClusters

Groups of sectors that are addressed as a Groups of sectors that are addressed as a groupgroup

Makes storage access quicker since there Makes storage access quicker since there are fewer units to addressare fewer units to address

Allows larger drives to be addressedAllows larger drives to be addressed Wastes some space when cluster is not Wastes some space when cluster is not

completely fullcompletely full Larger clusters are more wastefulLarger clusters are more wasteful

Default Cluster SizesDefault Cluster Sizes

Each file system has its own default Each file system has its own default cluster size rules (FAT16, FAT32, NTFS)cluster size rules (FAT16, FAT32, NTFS)

Cluster size can vary from 1 to 64 sectorsCluster size can vary from 1 to 64 sectors Generally, smaller drive has smaller Generally, smaller drive has smaller

cluster sizecluster size Refer to Tables 10.1, 10.2, and 10.3 in Refer to Tables 10.1, 10.2, and 10.3 in

textbooktextbook

Common File SystemsCommon File Systems

FAT16FAT16 FAT32FAT32 NTFS 4NTFS 4 NTFS 5NTFS 5

FAT FormattingFAT Formatting

Creates the volume boot record: Creates the volume boot record: Every logical drive has oneEvery logical drive has one Holds information about the partition Holds information about the partition Stores the boot files if a bootable driveStores the boot files if a bootable drive Written to the first sector of the logical disk Written to the first sector of the logical disk

(the (the boot sectorboot sector)) At startup, OS looks to the boot sector to see At startup, OS looks to the boot sector to see

if it contains startup filesif it contains startup files

FAT FormattingFAT Formatting

Creates the File Allocation TableCreates the File Allocation Table Small databaseSmall database Two copies of it, for redundancyTwo copies of it, for redundancy Tracks only the first cluster of each fileTracks only the first cluster of each file Tracks only files and folders in the root Tracks only files and folders in the root

directorydirectory

FAT FormattingFAT Formatting

Reads information from low-level format Reads information from low-level format about physical defects to avoid in disk about physical defects to avoid in disk surfacesurface

Creates the root directoryCreates the root directory Top-level folderTop-level folder All others are placed hereAll others are placed here

FAT16 versus FAT32FAT16 versus FAT32

FAT16FAT16 Original FAT file systemOriginal FAT file system Uses 16-bit binary numbers to identify each Uses 16-bit binary numbers to identify each

clustercluster FAT32FAT32

Improved versionImproved version Uses 32-bit binary numbers to identify each Uses 32-bit binary numbers to identify each

clustercluster Drive sizes can be larger because there are Drive sizes can be larger because there are

more numbers available for cluster IDsmore numbers available for cluster IDs

OS Compatibility of FATOS Compatibility of FAT

FAT16: FAT16: All MS-DOS and Windows versionsAll MS-DOS and Windows versions

FAT32:FAT32: No support in MS-DOS, Windows NT 4.0, or No support in MS-DOS, Windows NT 4.0, or

Windows 95Windows 95 Windows 95C provides limited support (no Windows 95C provides limited support (no

conversion utility)conversion utility) Windows 98 and higher provide full supportWindows 98 and higher provide full support

NTFSNTFS

New Technology File SystemNew Technology File System Developed for Windows NT (NTFS 4)Developed for Windows NT (NTFS 4) Improved for Windows 2000 and higher Improved for Windows 2000 and higher

(NTFS 5)(NTFS 5) 32-bit file system32-bit file system More sophisticated security permissionsMore sophisticated security permissions Encryption (NTFS 5)Encryption (NTFS 5)

NTFS FeaturesNTFS Features

Volume Boot RecordVolume Boot Record Equivalent to Volume Boot Record in FAT32Equivalent to Volume Boot Record in FAT32

Master File TableMaster File Table Equivalent to File Allocation TableEquivalent to File Allocation Table

System FilesSystem Files No stand-alone command interpreterNo stand-alone command interpreter User interface separate from OS kernelUser interface separate from OS kernel

OS Compatibility of NTFSOS Compatibility of NTFS

No support in MS-DOS or 9x versions of No support in MS-DOS or 9x versions of WindowsWindows

NTFS 4 supported in Windows NT 4.0NTFS 4 supported in Windows NT 4.0 NTFS 5 supported in Windows 2000 and NTFS 5 supported in Windows 2000 and

XPXP Conversion done automatically when Conversion done automatically when

upgrading from NT 4.0 to 2000 or XPupgrading from NT 4.0 to 2000 or XP