cd floppy, hard disk drive
TRANSCRIPT
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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: 33 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
Ultra DMA Mode 6: 133 MBps
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
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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