1. CDROM, Floppy and Hard Disk Structure
Plus some basic concepts

2. Table of Contents CD Floppy Disk 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
3½ Inch (2HD) Disks
Hard Disk
Some Basic Concepts
Boot Sector
Cluster
FAT
NTFS

3. PART 1
CD-ROM

5. 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
Compact disc Interactive (CD-I)
Compact Disc Television (CD-TV)
Compact Disc Recording (CD-R)
Digital Video Disc (DVD)

6. 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

7. CD Layers (cont’d)

8. 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

9. 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.

11. 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.

12. 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

13. CD Data Recording
Information is recorded on a CD using a series of bumps
Laser gun
Controller
curcuit
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

14. 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

15. Data Reading
Laser gun
Lens
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

16. 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)

17. 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

18. How The CD Drive Works (cont’d)

19. Information transfer rate
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
Information transfer rate 1X
150 Kbytes/s 2X
300 Kbytes/s …

20. 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 m/s (±0.01m/s)

21. 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

22. CD File Systems (cont’d)
2. 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

23. CD File Systems (cont’d)
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
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

24. 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

25. 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

26. 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

27. CD-RW Recording (cont’d)
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

28. 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

29. 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 microns minimum on CDs)
These technologies allow DVDs to store large amounts of data

30. 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

31. 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.

33. PART 2
Blu-ray VS HD-DVD

34. 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 feature-length video discs and additional layers possible later.

35. 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 are backward compatible with DVD and CD.

36. 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.

37. USB speed USB 1.0 – speed 1.5 Mb/s USB 1.1 – speed 12 Mb/s
USB 3.0 – speed 5 Gb/s

38. Hard disk drive Disk platter Read/Write head Head arm/Head slider
Head actuator mechanism
Spindle motor
Logic board
Air filter
Cables & Connectors

39. 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

40. 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

41. 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

42. 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

43. 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

44. 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

45. NTFS (cont’d) 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

46. 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

47. ATA Overview IDE - International Development Enterprises Cable
Keywords
Speed
Max size
ATA-1
40-pin
PIO and DMA
3.3 MBps to 8.3 MBps
504 MB
ATA-2
EIDE ATAPI
11.1 MBps to 16.6 MBps
8.4 GB
ATA-3
SMART
ATA-4
Ultra
16.7 MBps to 33.3 MBps
INT13
BIOS Upgrade
137 GB
ATA-5
40-pin 80-wires
ATA/33 ATA/66
44.4 MBps to 6.6 MBps
ATA-6
Big Drive
100 MBps
144 PB
ATA-7
80-wires 7-pin
ATA/133 SATA
133 MBps to 300 MBps
IDE - International Development Enterprises

48. 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)

49. 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

50. ATA-3 Self-Monitoring Analysis and Reporting Technology
S.M.A.R.T.
No real change in other stats

51. ATA-4 Introduced Ultra DMA Modes Ultra DMA Mode 2 also called ATA/33
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

52. 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

53. ATA-5 Introduced newer Ultra DMA Modes Ultra DMA Mode 3: 44.4 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

54. 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

55. 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

56. Serial ATA Hot-swappable Can have as many as eight SATA devices
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 inches compared to 18 inches for PATA cables

57. Serial ATA More on SATA eSATA
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
External SATA
Extends SATA bus to external devices
eSATA Port

58. SCSI Small Computer System Interface

59. 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

60. 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

61. 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

62. 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

63. 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
Make sure you can look at any SCSI device and understand how to set its SCSI ID!

64. 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 = Off, Off, Off, On
Device 7 = Off, On, On, On
Device 15 = On, On, On, On
Host adapters often set to 7 or 15 but can be changed

65. 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
Discussion Point
Termination
All electronic signals can reflect back (or echo) along the wire. On some systems, such as SCSI and coaxial networks, this can cause chaos, as devices do not know what signal to listen to. A terminator is basically a resistor that absorbs the signal to prevent it from reflecting back. All SCSI chains, without exception, have to be terminated at both ends of the chain, but never in the middle.

66. Protecting Data with RAID

67. 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

68. RAID Level 0 Disk striping Not fault tolerant
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

69. 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

70. RAID Levels 2 to 4 RAID 2 RAID 3 and 4
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

71. 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
Software-based RAID 5

72. RAID 5 (Stripe with Parity)
Decimal 22 21 20 4 2 1 3
Decimal 21 20
Odd Parity 2 1 3 1
Data 1
Data 1
Parity

73. RAID Level 6 Super disk striping with distributed parity
RAID 5 with asynchronous and cached data capability
The CompTIA A+ Certification exams are interested only in your understanding RAID levels 0, 1, and 5. I’m unaware of anyone actually using RAID levels 2, 3, or 4 in modern systems. Just be aware that these other levels of RAID exist.

74. 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

75. Hardware vs. Software Hardware RAID Software RAID Dedicated controller
Operating system views it as single volume
Software RAID
Operating system recognizes all individual disks
Combines them together as single volume

76. 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

77. THANK YOU