CDROM, Floppy and Hard Disk
Structure
Plus some basic concepts
Table of Contents
 CD
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History
Structure
Data Recording
How The CD Drive Works
CD File Systems
Multiple Sessions
CD-ReWritable (CD-RW)
DVD
 Floppy Disk
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History
Structure
Data Recording/Retrieval
Formatting
3½ Inch (2HD) Disks
Hard Disk
Some Basic Concepts
• Boot Sector
• Cluster
• FAT
• NTFS
PART 1
CD-ROM
www.themegallery.com
History
• Compact Disc - Digital Audio (CD-DA), the original CD
specification developed by Philips and Sony in 1980
• Specifications were published in Red 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
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Compact disc Interactive (CD-I)
Compact Disc Television (CD-TV)
Compact Disc Recording (CD-R)
Digital Video Disc (DVD)
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 of
reflective metal (usually
aluminum) on top of the
polycarbonate
• Then a thin layer of some
protective material covering the
reflective metal
• A label or some screened
lettering on top of protective
material
CD Layers (cont’d)
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 uses
light to record data in a
tightly packed form
Structure (cont’d)
• 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 from
0.9 to 3.3 microns.
– The distance between the
spiral is 1.6 micron.
– Track density on a CDROM is
about 16,000 tracks per inch.
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 hard
polycarbonate
• It is possible to carefully clean
and even to polish this surface
to remove fingerprints and even
scratches
• Many flaws on the
polycarbonate surface will
simply go unread.
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
CD Data Recording
• Information is
recorded on a CD
using a series of
bumps
• 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
Laser
gun
Controller
curcuit
Data Recording (cont’d)
• 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 is
mastered, this is why
its called CD-ROM
Data Reading
Lens
Laser
gun
Prism
Sensitive
diode
• 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 “1”
signal
How The CD Drive Works
• A motor rotates the CD
• The rotational speed varies so
as to maintain a constant
linear velocity (the disk is
rotated faster when its inner
"SPIRALS" are being read)
How The CD Drive Works (cont’d)
• 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
How The CD Drive Works (cont’d)
CD-ROM Drive Speed
• The CD-ROM drives are classified by their rotational 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
1X
2X
Information transfer rate
150 Kbytes/s
300 Kbytes/s
…
…
CD Physical Specifications
Diameter
120mm ±0.3mm
Transparent Layer Thickness
1.2mm ±0.1mm
Total Thickness
1.1mm - 1.5mm
Transparent 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)
CD File Systems
1.
ISO-9660
The base standard defines three levels of compliance
– Level 1 limits file names to 8+3 format. Many special
characters (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
CD File Systems (cont’d)
2.
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Rock Ridge
Extensions to ISO-9660 file system
Favored in the Unix world
Lifts file name restrictions, but also allows Unix-style
permissions and special files to be stored on the CD
Machines that don't support Rock Ridge can still read
the 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
CD File Systems (cont’d)
3.
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•
•
4.
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
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
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 some
space is reserved for timing and other information
• Each session written has an overhead of approximately
20MB per session
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
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
CD-RW Recording (cont’d)
• The laser beam melts the crystals and makes them noncrystalline (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
DVD
• Digital Versatile Disk (Formerly Digital Video Disk)
• 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
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
DVD (cont’d)
• 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
DVD (cont’d)
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-Layer
Capacity 9,4 GB.
DVD-18
17.1GB Double-Side, Dual-Layer
Capacity 17,1 GB.
PART 2
Blu-ray VS HD-DVD
Blu-ray disc
• Blu-ray Disc (official
abbreviation BD) is an optical
disc 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 GB
per layer, with dual layer discs
(50 GB) the norm for featurelength video discs and
additional layers possible later.
HD - DVD
• HD DVD-ROM, HD DVD-R and
HD DVD-RW have a single-layer
capacity of 15 GB, and a duallayer capacity of 30 GB.
• HD DVD-RAM has a singlelayer 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 are
backward compatible with DVD
and CD.
USB Flash
drive
• A USB flash drive consists of
a 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.
USB speed
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USB 1.0 – speed 1.5 Mb/s
USB 1.1 – speed 12 Mb/s
USB 2.0 – speed 480 Mb/s
USB 3.0 – speed 5 Gb/s
Hard disk drive
• Disk platter
• Read/Write
head
• Head arm/Head
slider
• Head actuator
mechanism
• Spindle motor
• Logic board
• Air filter
• Cables &
Connectors
Hard Disk
• Fixed and
removable
• Fast (disk
rotates at 60
to 200 times
per second)
• Currently 20 – 2 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
Boot Sector (Boot Record)
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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
DOS/Win Formatted Disk
• A DOS/Win formatted floppy/hard disk’s 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
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
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
NTFS
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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
NTFS (cont’d)
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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 for
recording files
• At clearing the usual area, MFT can be extended again
Hard Drive Interfaces
• ATA interfaces dominate today’s 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
ATA Overview
ATA-1
Cable
40-pin
Keywords
PIO and DMA
Speed
3.3 MBps to 8.3 MBps
Max size
504 MB
ATA-2
40-pin
11.1 MBps to 16.6 MBps
8.4 GB
ATA-3
ATA-4
INT13
40-pin
40-pin
EIDE
ATAPI
SMART
Ultra
BIOS Upgrade
11.1 MBps to 16.6 MBps
16.7 MBps to 33.3 MBps
8.4 GB
8.4 GB
137 GB
ATA-5
40-pin
80-wires
40-pin
80-wires
40-pin
ATA/33 ATA/66
44.4 MBps to 6.6 MBps
137 GB
Big Drive
100 MBps
144 PB
ATA/133
133 MBps to 300 MBps
144 PB
ATA-6
ATA-7
80-wires 7-pin SATA
IDE - International Development Enterprises
ATA-1
• Programmable I/O
(PIO)—traditional data
transfer
– 3.3 MBps to 8.3
MBps
• DMA—direct memory
access
– 2.1 MBps to 8.3
MBps
• Allowed two drives
(one master, one slave)
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
• Self-Monitoring Analysis and Reporting
Technology
– S.M.A.R.T.
• No real change in other stats
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
INT13-Interrupt Extensions
• ATA-1 standard actually written for hard
drives 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
• 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 connector—to controller
– Gray connector—slave drive
– Black connector—master drive
ATA/66 cable
ATA-6
• “Big Drives” introduced
• Replaced INT13 & 24-bit LBA to 48-bit LBA
• Increased maximum size to 144 PB
– 144,000,000 GB
• Introduced Ultra DMA 5
– Ultra DMA Mode 5: 100 MBps ATA/100
– Used same 40-pin, 80-wire cables as ATA-5
ATA-7
• Introduced Ultra DMA 6
– Ultra DMA Mode 6: 133 MBps
ATA/133
– Used same 40-pin, 80-wire cables as
ATA-5
– Didn’t really take off due to SATA’s
popularity
• Introduced Serial ATA (SATA)
– Increased throughput to 150 MBps to
300 MBps
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
• More on SATA
– PATA device my be connected to SATA
using a SATA bridge
– Can have as many as eight SATA devices
• Add more SATA functionality via a PCI card
• eSATA
eSATA Port
– External SATA
– Extends SATA bus to external devices
SCSI
Small Computer System Interface
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 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
Internal Devices
• Internal SCSI devices are installed inside
the PC and connect to the host adapter
through the internal connector
• Internal devices use a 68-pin ribbon cable
• Cables can be connected to multiple devices
External Devices
• External SCSI devices are connected to host adapter
to external connection of host adapter
• External devices have two connections in the back, to
allow for daisy-chaining
• A standard SCSI chain can connect 15 devices,
including the host adapter
SCSI IDs
• Each SCSI device
must have a unique
SCSI ID
• The values of ID
numbers range from
0 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
• The SCSI ID for a particular device can be
set by configuring jumpers, switches, or
even dials
• Use your hexadecimal knowledge to set the
device ID
– Device 1 = 0 0 0 1
On
– Device 7 = 0 1 1 1
On
– Device 15 = 1 1 1 1
On
Off, Off, Off,
Off, On, On,
On, On, On,
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 be
terminated
• Most manufacturers
build SCSI devices
that self-terminate
Protecting Data
with RAID
Protecting Data
• The most important part of a PC is the data
it holds
– Companies 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 fails
– Redundant Array of Inexpensive Disks (RAID)
is one such technology
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
• Disk mirroring/duplexing is the process of writing the same data to
two drives at the
same time
–
–
–
–
Requires two drives
Produces an exact mirror of the primary drive
Mirroring uses the same controller
Duplexing uses separate controllers
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
• Disk striping with distributed parity
– Distributes data and parity evenly across the
drives
– Requires at least three drives
– Most common RAID implementation
Softwarebased RAID 5
RAID 5 (Stripe with Parity)
Decimal
0
1
2
3
4
22
4
0
0
0
0
1
21
2
0
0
1
1
0
20
1
0
1
0
1
0
Decimal
21
20
0
1
2
3
2
0
0
1
1
1
0
1
0
1
Odd
Parity
1
0
0
1
0
0
1
0
1
0
1
0
0
1
1
1
Data
Data
Parity
RAID Level 6
• Super disk striping with distributed parity
– RAID 5 with asynchronous and cached data
capability
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
• Hardware RAID
– Dedicated controller
– Operating system views
it as single volume
• Software RAID
– Operating system
recognizes all individual
disks
– Combines them together
as single volume
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