CD Floppy, Hard Disk Drive

7/29/2019 CD Floppy, Hard Disk Drive

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CDROM, Floppy and Hard Disk

Structure

Hardware ServicingMichael Angelo D. Brogada, MIT


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Table of Contents

CD

History

Structure

Data Recording

How The CD Drive Works

CD File Systems

Multiple Sessions

CD-ReWritable (CD-RW) DVD

Floppy Disk

History

Structure

Data Recording/Retrieval

Formatting

3 Inch (2HD) Disks

Hard Disk

Some Basic Concepts Boot Sector

Cluster

FAT

NTFS


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PART 1CD-ROM


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www.themegallery.com


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History

Compact Disc - Digital Audio (CD-DA), the original CD

specification developed by Philips and Sony in 1980

Specifications were published inRed Book, continued to be

updated (lastest version in 1999)

In 1985 a standard for the storage of computer data by Sony

and Philips, CD-ROM (Compact Disc Read Only Memory)

Developments in the technology have been ongoing and rapid

Compact disc Interactive (CD-I)

Compact Disc Television (CD-TV)

Compact Disc Recording (CD-R)

Digital Video Disc (DVD)


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Structure The thickness of a CD can vary between 1.1 and 1.5mm

CDROM can store 720 MB of data.

A CD consists of four layers The biggest part is clear

polycarbonate (nominally

1.2mm)

There is a very thin layer ofreflective metal (usuallyaluminum) on top of the

polycarbonate

Then a thin layer of some

protective material covering thereflective metal

A label or some screenedlettering on top of protectivematerial


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CD Layers (contd)


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Structure

A CDROM Drive uses a

small plastic-encapsulated

disk that can store data This information is retrieved

using a Laser Beam

A CD can store vast amounts

of information because it useslight to record data in a

tightly packed form


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Structure (contd) On surface of CDROM,

laser beam to use to was be

"punched" to according the

spiral called the pits. These

positions do not have

"punch" as land.

The 0.12 micron deep pit,

approximately 0.6 microns

wide.

The pit and land length from0.9 to 3.3 microns.

The distance between the

spiral is 1.6 micron.

Track density on a CDROM isabout 16,000 tracks per inch.


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CD Safety

The label side of a CD is the

most vulnerable part of the disk

The other side is protected by

the thick (1.2mm) and hardpolycarbonate

It is possible to carefully clean

and even to polish this surface

to remove fingerprints and evenscratches

Many flaws on the

polycarbonate surface will

simply go unread.


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CD vs. Magnetic Media

In Magnetic Media (like floppy/hard

disk) the surface is arranged into

concentric circles called tracks

Number of sectors per track is

constant for all tracks

The CD has one single track, starts at

the center of the disk and spirals out

to the circumference of the disk

This track is divided into sectors of

equal size


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CD Data Recording

In the recording, Lazer

gun was used to write data

to disk

Signal corresponding to 0=> laser off.

Signal corresponding to 1

=> laser on => burned disk

surface into a point of

losing the ability to reflect

Information isrecorded on a CD

using a series of

bumps

Laser

gun

Controller

curcuit


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Data Recording (contd)

The unmarked areas between pits are called "lands

Lands are flat surface areas

The information is

stored permanently as

pits and lands on the

CD-ROM. It cannot

be changed once the

CD-ROM ismastered, this is why

its called CD-ROM


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Data Reading

Laser reflection on

rotating disk

surface, the pit

will be lost

reflected rays =>that is 0 signal,

the land they

received reflected

rays => that is 1signal

Laser

gun

Lens

Prism

Sensitive

diode


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How The CD Drive Works

A motor rotates the CD

The rotational speed varies so

as to maintain a constant

linear velocity (the disk isrotated faster when its inner

"SPIRALS" are being read)


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How The CD Drive Works (contd)

A laser beam is shone onto the surface of the disk

The light is scattered by the pits and reflected by the lands,

these two variations encode the binary 0's and 1's

A light sensitive diode picks up the reflected laser light and

converts the light to digital data


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How The CD Drive Works (contd)


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CD-ROM Drive Speed

The CD-ROM drives are classified by theirrotational speed

Based on the original speed of a CD-Audio (e.g. A "2X"

CD-ROM drive will run at twice the speed of a CD- Audio)

Speed Information transfer rate

1X 150 Kbytes/s2X 300 Kbytes/s


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CD Physical Specifications

Diameter 120mm 0.3mm

Transparent Layer Thickness 1.2mm 0.1mm

Total Thickness 1.1mm - 1.5mmTransparent Layer Index of

Refraction

1.55 0.10

Reflectance of Metal Layer

through Transparent Layer

70% minimum

Laser Wavelength 780nm 10nm

Track Pitch 1.6 micron 0.1 micron

Scanning Linear Velocity 1.20m/s - 1.40m/s (0.01m/s)


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CD File Systems

1. ISO-9660

The base standard defines three levels of compliance

Level 1 limits file names to 8+3 format. Many specialcharacters (space, hyphen, equals, and plus) are

forbidden

Level 2 and 3 allow longer filenames (up to 31) and

deeper directory structures (32 levels instead of 8)

Level 2 and 3 are not usable on some systems, special

MS-DOS


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CD File Systems (contd)

2. Rock Ridge

Extensions to ISO-9660 file system

Favored in the Unix world

Lifts file name restrictions, but also allows Unix-stylepermissions and special files to be stored on the CD

Machines that don't support Rock Ridge can still readthe files because it's still an ISO-9660 file system (they

won't see the long forms of the names) UNIX systems and the Mac support Rock Ridge

DOS and Windows currently don't support it


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CD File Systems (contd)

3. Joliet

Favored in the MS Windows world

Allows Unicode characters to be used for all text fields(including file names and the volume name)

Disk is readable as ISO-9660, but shows the long

filenames under MS Windows

4. HFS (Hierarchical File System)Used by the Macintosh in place of the ISO-9660, making

the disk unusable on systems that don't support HFS


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Multiple Sessions

Allows CDs to be written more than once (not re-written)

Some CD writers support this feature

About 640MB of data can be written to the CD, as somespace is reserved for timing and other information

Each session written has an overhead of approximately

20MB per session


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CD-ReWritable (CD-RW)

It is essentially CD-R

Allows discs to be written and

re-written up to 1000 times The storage capacity is the

same as that for CD-R

Based on phase-change

technology. The recording layer is a

mixture of silver, indium,

antimony and tellurium


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CD-RW Recording Process

The recording layer is polycrystalline

The laser heats selected areas of the recording track to the

recording layer's melting point of 500 to 700 degrees Celsius


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CD-RW Recording (contd)

The laser beam melts the crystals and makes them non-

crystalline (amorphous phase)

The medium quickly cools, locking in the properties of the

heated areas The amorphous areas have a lower reflectivity than the

crystalline areas

This creates a pattern which can be read as pits and lands

of the traditional CD To erase a CD-RW disc, the recording laser turns the

amorphous areas back into crystalline areas


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DVD

Same size (120mm) and

thickness (1.2mm) as CD

Improvements in the

logarithms used for error

correction

Much greater data accuracy

using smaller Error

Correction Codes (ECC)

More effective use of the

track space

Digital Versatile Disk(Formerly Digital Video Disk)


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DVD vs. CD

DVD uses a tighter spiral (track or helix) with only 0.74

microns between the tracks (1.6 microns on CDs)

DVD recorders use a laser with a smaller wavelength, 635nm

or 650 nm (visible red light) vs. 780nm (infrared) for CDs

DVD has smaller "burns" (pits) in the translucent dye layer

(0.4 microns minimum vs. 0.83 microns minimum on CDs)

These technologies allow DVDs to store large amounts of data


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DVD (contd)

Standard single-sided DVDs store up to 4.7GB of data

Dual-sided discs hold about 8.5GB of data (9.4GB for

back-to-back layers dual-sided discs)

In back-to-back layers discs, it must be turned over to

access the data on the reverse side

DVD uses MPEG2 compression for high quality pictures

DVD drives have a much faster transfer rate than CD drives DVD-ROM drives will read and play existing CD-ROM

and CD-A disks


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DVD (contd)

Types Characteristics

DVD-5 4.7GB Single-Side, Single-Layer

capacity 4,7 GB.

DVD-9 8.5GB Single-Side, Dual-Layer

Capacity 8,5 GB.

DVD-10 9.4GB Double-Side, Single-LayerCapacity 9,4 GB.

DVD-18 17.1GB Double-Side, Dual-Layer

Capacity 17,1 GB.


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PART 2Blu-ray VS HD-DVD


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Blu-ray disc Blu-ray Disc (official

abbreviation BD) is an opticaldisc storage medium designed

to replace the DVD format.

The standard physical medium

is a 12 cm plastic optical disc,

the same size as DVDs and

CDs.

Blu-Ray Discs contain 25 GBper layer, with dual layer discs

(50 GB) the norm for feature-

length video discs and

additional layers possible later.


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HD - DVD HD DVD-ROM, HD DVD-R and

HD DVD-RW have a single-layer

capacity of 15 GB, and a dual-

layer capacity of 30 GB.

HD DVD-RAM has a single-

layer capacity of 20 GB. Like the

original DVD format, the data

layer of an HD DVD is 0.6 mm

below the surface to physically

protect the data layer from

damage.

All HD DVD players arebackward compatible with DVD

and CD.

USB Fl h


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USB Flash

drive

A USB flash drive consists ofa flash memory data storage

device integrated with a USB

(Universal Serial Bus)

interface.

USB flash drives are typically

removable and rewritable, and

physically much smaller than a

floppy disk.

Most weigh less than 30 gram.Storage capacities in 2010 can

be as large as 256 GB with

steady improvements in size

and price per capacity

expected.

d


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USB speed

USB 1.0speed 1.5 Mb/s

USB 1.1speed 12 Mb/s

USB 2.0speed 480 Mb/s

USB 3.0speed 5 Gb/s

H d di k d i


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Hard disk drive

Disk platter

Read/Write head Head arm/Head

slider

Head actuatormechanism

Spindle motor

Logic board

Air filter Cables &

Connectors


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Hard Disk

Fixed andremovable

Fast (disk

rotates at 60

to 200 timesper second)

Currently 202 TB (may be limited by the version of the

operating system)

Like floppies, uses the magnetic properties of the coating

material, but the technology is different


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Boot Sector (Boot Record)

A vital sector, disk will be unusable if this sector damages

MBR at CHS 0, 0, 1 in hard disks, contains Partition Table

Each partition has its own boot sector too

Each operating system has its own boot sector format

For Booting, Bootstrap Loader loads Boot Sector data it in a

particular address of memory (0000:7C00h) and sets the PC

In hard disks, the small program in MBR attempts to locate

an active (bootable) partition in partition table

If found, the boot record of that partition is read into memory

(location 0000:7C00) and runs


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DOS/Win Formatted Disk

A DOS/Win formatted floppy/hard disks Boot Sector contains

A jump and a NOP (No Operation Performed) op-code

(operation code)

BPB (BIOS Parameter Block)

- Sectors per cluster

- Number of Root directory entries

- Sectors per FAT

- Volume Label

-

A program, to load OS if bootable/show error msg if not in

floppies, to locate the active partition in hard disks

Error messages


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Cluster

Data units of disk must be addressed, which units belong

to which file / are free / are damaged (bad sectors) /

On disks having large capacity, purposing one sector as a

unit makes addressing table so large Cluster is defined

Represents the smallest amount of disk space that OS can

be allocated

The smaller the cluster size, the more efficiently disk

space usage, the more number of bits to address one unit

The number of sectors per cluster is stored in the

Boot Record


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FAT

FAT-12/FAT-16/FAT-32 are Microsoft favorite File

Allocation Tables (before NTFS)

FAT-12 uses 12 bits for addressing, a max. of 4096 units,

considering one sector as a cluster, 2MB can be addressed

FAT-16 with max.(128) sectors/cluster (64KB cluster size

wasting large amount of disk space) up to 4GB, this is

why Win95 cannot support more than 4GB partiotions

FAT-32, the same system,

32 bit fields for addressing


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NTFS

NT File System

Better performance

Less wasted space

More security

Supports all sizes of

clusters (512b - 64 KB)

The 4 KB cluster is somehow standard Practically no partition size limitation

Very flexible, all the system files can be relocated, except

the first 16 MFT (Master File Table) elements


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NTFS (contd)

NTFS disk is symbolically divided into two parts

The first 12% is assigned to MFT area

The rest 88% represents usual space for files storage

MFT area can simply reduce if needed, clearing the space forrecording files

At clearing the usual area, MFT can be extended again


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Hard Drive Interfaces

ATA interfaces dominate todays market

Many changes throughout years

Parallel ATA (PATA) historically prominent

Serial ATA (SATA) since 2003

Small Computer System Interface (SCSI) Pronounced Scuzzy

Used in many high-end systems


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ATA Overview

Cable Keywords Speed Max sizeATA-1 40-pin PIO and DMA 3.3 MBps to 8.3 MBps 504 MB

ATA-2 40-pin EIDE

ATAPI

11.1 MBps to 16.6 MBps 8.4 GB

ATA-3 40-pin SMART 11.1 MBps to 16.6 MBps 8.4 GB

ATA-4 40-pin Ultra 16.7 MBps to 33.3 MBps 8.4 GB

INT13 BIOS Upgrade 137 GB

ATA-5 40-pin

80-wires

ATA/33 ATA/66 44.4 MBps to 6.6 MBps 137 GB

ATA-6 40-pin

80-wires

Big Drive 100 MBps 144 PB

ATA-7 40-pin

80-wires 7-pin

ATA/133

SATA

133 MBps to 300 MBps 144 PB

IDE - International Development Enterprises


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ATA-1

Programmable I/O

(PIO)traditional datatransfer

3.3 MBps to 8.3

MBps DMAdirect memory

access

2.1 MBps to 8.3

MBps

Allowed two drives

(one master, one slave)

ATA 2


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ATA-2 Commonly called EIDE (though a

misnomer)

Added second controller to allow for four

drives instead of only two

Increased size to 8.2 GB

Added ATAPI

Could now use CD drives

ATA 3


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ATA-3

Self-Monitoring Analysis and Reporting

TechnologyS.M.A.R.T.

No real change in other stats


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ATA-4

Introduced Ultra DMA Modes

Ultra DMA Mode 0: 16.7 MBps

Ultra DMA Mode 1: 25 MBps


Ultra DMA Mode 2 also called ATA/33


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INT13-Interrupt Extensions

ATA-1 standard actually written for harddrives up to 137 GB

BIOS limited it to 504 MB due to cylinder,

head, and sector maximums

ATA-2 implemented LBA (Logical block

addressing) to fool the BIOS, allowing drives

to be as big as 8.4 GB

INT13 Extensions extended BIOS

commands

Allowed drives as large as 137 GB

ATA 5


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ATA-5

Introduced newer Ultra DMA Modes

Ultra DMA Mode 3: 44.4 MBps Ultra DMA Mode 4: 66.6 MBps

Ultra DMA Mode 4 also called ATA/66

Used 40-pin cable, but had 80 wires

Blue connectorto controller

Gray connectorslave drive Black connectormaster drive

ATA/66 cable

ATA-6


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ATA 6

Big Drives introduced

Replaced INT13 & 24-bit LBA to 48-bit LBA

Increased maximum size to 144 PB144,000,000 GB

Introduced Ultra DMA 5

Ultra DMA Mode 5: 100 MBps ATA/100

Used same 40-pin, 80-wire cables as ATA-5


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ATA-7

Introduced Ultra DMA 6


ATA/133

Used same 40-pin, 80-wire cables as

ATA-5

Didnt really take off due to SATAs

popularity

Introduced Serial ATA (SATA) Increased throughput to 150 MBps to

300 MBps

Serial ATA


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Serial ATA

Serial ATA (SATA) creates a point-to-point

connection between the device and the controller

Hot-swappable

Can have as many as eight SATA

devices

Thinner cables resulting in better

airflow and cable control in the PC

Maximum cable length of

39.4 inches compared to

18 inches for PATA cables

Serial ATA


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Serial ATA More on SATA

PATA device my be connected to SATAusing a SATA bridge

Can have as many as eight SATA devices Add more SATA functionality via a PCI card

eSATA

External SATA

Extends SATA bus to external devices

eSATA Port


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SCSI

Small Computer System Interface

SCSI


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SCSI Pronounced Scuzzy

Been around since 70s

Devices can be internal or external

Historically the choice for RAID

Faster than PATA

Could have more than four drives

SATA replacing SCSI in many applications

SCSI Ch i


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SCSI Chains

A SCSI chain is a series of SCSI devices working

together through a host adapter

The host adapter is a device that attaches the SCSI

chain to the PC

All SCSI devices are divided into internal and

external groups

The maximum number of devices, including the

host adapter, is 16

l i


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Internal Devices Internal SCSI devices are installed inside

the PC and connect to the host adapterthrough the internal connector

Internal devices use a 68-pin ribbon cable

Cables can be connected to multiple devices

External Devices


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External Devices

External SCSI devices are connected to host adapterto external connection of host adapter

External devices have two connections in the back, toallow fordaisy-chaining

A standard SCSI chain can connect 15 devices,including the host adapter

SCSI IDs


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Each SCSI device

must have a unique

SCSI ID

The values of ID

numbers range from0 to 15

No two devices connected to a single host adapter can

share the same ID number

No order for the use of SCSI IDs, and any SCSI device

can have any SCSI ID

SCSI IDs


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SCSI IDs

The SCSI ID for a particular device can be

set by configuring jumpers, switches, oreven dials

Use your hexadecimal knowledge to set thedevice ID

Device 1 = 0 0 0 1 Off, Off, Off,

On

Device 7 = 0 1 1 1 Off, On, On,

On

Device 15 = 1 1 1 1 On, On, On,

On

T i ti


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Termination Terminators are used to prevent a signal reflection that can corrupt the

signal

Pull-down resistors are usually used as terminators

Only the ends of the

SCSI chains need to beterminated

Most manufacturersbuild SCSI devicesthat self-terminate

P t ti D t


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Protecting Data

with RAID

Protecting Data


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The most important part of a PC is the data

it holdsCompanies have gone out of business because

of losing data on hard drives

Hard drives will eventually develop faults

Fault tolerance allows systems to operate

even when a component failsRedundant Array of Inexpensive Disks (RAID)

is one such technology

g

RAID Level 0


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RAID Level 0

Disk striping

Writes data across multiple drives at once

Requires at least two hard drives

Provides increased read and writes

Not fault tolerant If any drive fails,

the data is lost

RAID Level 1


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RAID Level 1

Disk mirroring/duplexing is the process of writing the same data to

two drives at thesame time

Requires two drives

Produces an exact mirror of the primary drive

Mirroring uses the same controller

Duplexing uses separate controllers

l


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RAID Levels 2 to 4 RAID 2

Disk striping with multiple parity drives

Not used

RAID 3 and 4

Disk striping with dedicated parity

Dedicated data drives and dedicated parity

drives

Quickly replaced by RAID 5

RAID Level 5


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Disk striping with distributed parity

Distributes data and parity evenly across thedrives

Requires at least three drives

Most common RAID implementation

Software-based RAID 5

RAID 5 (Stripe with Parity)


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RAID 5 (Stripe with Parity)

Decimal 22

21

20

4 2 1

0 0 0 0

1 0 0 1

2 0 1 0

3 0 1 1

4 1 0 0

Decimal 21

20

OddParity

2 1

0 0 0 1

1 0 1 0

2 1 0 0

3 1 1 1

0

01

1

Data

0

10

1

Data

1

00

1

Parity


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RAID Level 6

Super disk striping with distributed parity

RAID 5 with asynchronous and cached datacapability

Implementing RAID


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Implementing RAID

SCSI has been the primary choice in the

past

Faster than PATA

PATA allowed only four drives

SATA today viewed as comparable choice

Speeds comparable to SCSI

Dedicated SATA controllers can support up to

15 drives

Hardware vs Software


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Hardware vs. Software Hardware RAID

Dedicated controllerOperating system views

it as single volume

Software RAID

Operating system

recognizes all individual

disksCombines them together

as single volume

Personal RAID


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Personal RAID

ATA RAID controller chips have gone

down in price

Some motherboards are now shipping with

RAID built-in

The future is RAID

RAID has been around for 20 years but is now

less expensive and moving into desktop

systems

Documents

CD Floppy, Hard Disk Drive