Presentation on theme: "CDROM, Floppy and Hard Disk Structure"— Presentation transcript:
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 WorksCD File SystemsMultiple SessionsCD-ReWritable (CD-RW)DVDFloppy DiskHistoryStructureData Recording/RetrievalFormatting3½ Inch (2HD) DisksHard DiskSome Basic ConceptsBoot SectorClusterFATNTFS
5 HistoryCompact Disc - Digital Audio (CD-DA), the original CD specification developed by Philips and Sony in 1980Specifications 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 rapidCompact 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 layersThe biggest part is clear polycarbonate (nominally 1.2mm)There is a very thin layer of reflective metal (usually aluminum) on top of the polycarbonateThen a thin layer of some protective material covering the reflective metalA label or some screened lettering on top of protective material
8 StructureA CDROM Drive uses a small plastic-encapsulated disk that can store dataThis information is retrieved using a Laser BeamA 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 SafetyThe label side of a CD is the most vulnerable part of the diskThe other side is protected by the thick (1.2mm) and hard polycarbonateIt is possible to carefully clean and even to polish this surface to remove fingerprints and even scratchesMany flaws on the polycarbonate surface will simply go unread.
12 CD vs. Magnetic MediaIn Magnetic Media (like floppy/hard disk) the surface is arranged into concentric circles called “tracks”Number of sectors per track is constant for all tracksThe CD has one single track, starts at the center of the disk and spirals out to the circumference of the diskThis track is divided into sectors of equal size
13 CD Data RecordingInformation is recorded on a CD using a series of bumpsLaser gunControllercurcuitIn the recording, Lazer gun was used to write data to diskSignal 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 areasThe 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 ReadingLaser gunLensPrismSensitive diodeLaser 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 diskThe light is scattered by the pits and reflected by the lands, these two variations encode the binary 0's and 1'sA light sensitive diode picks up the reflected laser light and converts the light to digital data
19 Information transfer rate CD-ROM Drive SpeedThe CD-ROM drives are classified by their rotational speedBased 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)SpeedInformation transfer rate1X150 Kbytes/s2X300 Kbytes/s…
20 CD Physical Specifications Diameter120mm ±0.3mmTransparent Layer Thickness1.2mm ±0.1mmTotal Thickness1.1mm - 1.5mmTransparent Layer Index of Refraction1.55 ±0.10Reflectance of Metal Layer through Transparent Layer70% minimumLaser Wavelength780nm ±10nmTrack Pitch1.6 micron ±0.1 micronScanning Linear Velocity1.20m/s m/s (±0.01m/s)
21 CD File Systems1. ISO-9660The base standard defines three levels of complianceLevel 1 limits file names to 8+3 format. Many special characters (space, hyphen, equals, and plus) are forbiddenLevel 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 RidgeExtensions to ISO-9660 file systemFavored in the Unix worldLifts file name restrictions, but also allows Unix-style permissions and special files to be stored on the CDMachines 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 RidgeDOS and Windows currently don't support it
23 CD File Systems (cont’d) 3. JolietFavored in the MS Windows worldAllows 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 WindowsHFS (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 SessionsAllows CDs to be written more than once (not re-written)Some CD writers support this featureAbout 640MB of data can be written to the CD, as some space is reserved for timing and other informationEach session written has an overhead of approximately 20MB per session
25 CD-ReWritable (CD-RW) It is essentially CD-RAllows discs to be written and re-written up to 1000 timesThe storage capacity is the same as that for CD-RBased 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 polycrystallineThe 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 areasThe amorphous areas have a lower reflectivity than the crystalline areasThis creates a pattern which can be read as pits and lands of the traditional CDTo 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 CDImprovements in the logarithms used for error correctionMuch greater data accuracy using smaller Error Correction Codes (ECC)More effective use of the track space
29 DVD vs. CDDVD 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 CDsDVD 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 sideDVD uses MPEG2 compression for high quality picturesDVD drives have a much faster transfer rate than CD drivesDVD-ROM drives will read and play existing CD-ROM and CD-A disks
34 Blu-ray discBlu-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 - DVDHD 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 driveA 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 mechanismSpindle motorLogic boardAir filterCables & 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 damagesMBR at CHS 0, 0, 1 in hard disks, contains Partition TableEach partition has its own boot sector tooEach operating system has its own boot sector formatFor Booting, Bootstrap Loader loads Boot Sector data it in a particular address of memory (0000:7C00h) and sets the PCIn hard disks, the small program in MBR attempts to locate an active (bootable) partition in partition tableIf 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 containsA jump and a NOP (No Operation Performed) op-code (operation code)BPB (BIOS Parameter Block)Sectors per clusterNumber of Root directory entriesSectors per FATVolume Label…A program, to load OS if bootable/show error msg if not in floppies, to locate the active partition in hard disksError messages
42 ClusterData 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 definedRepresents the smallest amount of disk space that OS can be allocatedThe smaller the cluster size, the more efficiently disk space usage, the more number of bits to address one unitThe number of sectors per cluster is stored in theBoot Record
43 FATFAT-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 addressedFAT-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 partiotionsFAT-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 standardPractically no partition size limitationVery 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 areaThe rest 88% represents usual space for files storageMFT area can simply reduce if needed, clearing the space for recording filesAt clearing the usual area, MFT can be extended again
46 Hard Drive Interfaces ATA interfaces dominate today’s market Many changes throughout yearsParallel ATA (PATA) historically prominentSerial ATA (SATA) since 2003Small Computer System Interface (SCSI)Pronounced “Scuzzy”Used in many high-end systems
47 ATA Overview IDE - International Development Enterprises Cable KeywordsSpeedMax sizeATA-140-pinPIO and DMA3.3 MBps to 8.3 MBps504 MBATA-2EIDE ATAPI11.1 MBps to 16.6 MBps8.4 GBATA-3SMARTATA-4Ultra16.7 MBps to 33.3 MBpsINT13BIOS Upgrade137 GBATA-540-pin 80-wiresATA/33 ATA/6644.4 MBps to 6.6 MBpsATA-6Big Drive100 MBps144 PBATA-780-wires 7-pinATA/133 SATA133 MBps to 300 MBpsIDE - International Development Enterprises
48 ATA-1 Programmable I/O (PIO)—traditional data transfer 3.3 MBps to 8.3 MBpsDMA—direct memory access2.1 MBps to 8.3 MBpsAllowed 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 twoIncreased size to 8.2 GBAdded ATAPICould 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 MBpsUltra DMA Mode 1: 25 MBpsUltra DMA Mode 2: 33 MBpsUltra DMA Mode 2 also called ATA/33
52 INT13-Interrupt Extensions ATA-1 standard actually written for hard drives up to 137 GBBIOS limited it to 504 MB due to cylinder, head, and sector maximumsATA-2 implemented LBA (Logical block addressing) to fool the BIOS, allowing drives to be as big as 8.4 GBINT13 Extensions extended BIOS commandsAllowed 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/66Used 40-pin cable, but had 80 wiresBlue connector—to controllerGray connector—slave driveBlack connector—master driveATA/66 cable
54 ATA-6 “Big Drives” introduced Replaced INT13 & 24-bit LBA to 48-bit LBAIncreased maximum size to 144 PB144,000,000 GBIntroduced Ultra DMA 5Ultra DMA Mode 5: 100 MBps ATA/100Used 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-5Didn’t really take off due to SATA’s popularityIntroduced 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 controllerHot-swappableCan have as many as eight SATA devicesThinner cables resulting in better airflow and cable control in the PCMaximum 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 bridgeCan have as many as eight SATA devicesAdd more SATA functionality via a PCI cardeSATAExternal SATAExtends SATA bus to external deviceseSATA Port
59 SCSI Pronounced “Scuzzy” Been around since ’70s Devices can be internal or externalHistorically the choice for RAIDFaster than PATACould have more than four drivesSATA replacing SCSI in many applications
60 SCSI ChainsA SCSI chain is a series of SCSI devices working together through a host adapterThe host adapter is a device that attaches the SCSI chain to the PCAll SCSI devices are divided into internal and external groupsThe maximum number of devices, including the host adapter, is 16
61 Internal DevicesInternal SCSI devices are installed inside the PC and connect to the host adapter through the internal connectorInternal devices use a 68-pin ribbon cableCables can be connected to multiple devices
62 External DevicesExternal SCSI devices are connected to host adapter to external connection of host adapterExternal devices have two connections in the back, to allow for daisy-chainingA 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 15No two devices connected to a single host adapter can share the same ID numberNo order for the use of SCSI IDs, and any SCSI device can have any SCSI IDMake sure you can look at any SCSI device and understand how to set its SCSI ID!
64 SCSI IDsThe SCSI ID for a particular device can be set by configuring jumpers, switches, or even dialsUse your hexadecimal knowledge to set the device IDDevice 1 = Off, Off, Off, OnDevice 7 = Off, On, On, OnDevice 15 = On, On, On, OnHost adapters often set to 7 or 15 but can be changed
65 TerminationTerminators are used to prevent a signal reflection that can corrupt the signalPull-down resistors are usually used as terminatorsOnly the ends of the SCSI chains need to be terminatedMost manufacturers build SCSI devices that self-terminateDiscussion PointTerminationAll 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.
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 drivesHard drives will eventually develop faultsFault tolerance allows systems to operate even when a component failsRedundant Array of Inexpensive Disks (RAID) is one such technology
68 RAID Level 0 Disk striping Not fault tolerant Writes data across multiple drives at onceRequires at least two hard drivesProvides increased read and writesNot fault tolerantIf any drive fails, the data is lost
69 RAID Level 1Disk mirroring/duplexing is the process of writing the same data to two drives at the same timeRequires two drivesProduces an exact mirror of the primary driveMirroring uses the same controllerDuplexing uses separate controllers
70 RAID Levels 2 to 4 RAID 2 RAID 3 and 4 Disk striping with multiple parity drivesNot usedRAID 3 and 4Disk striping with dedicated parityDedicated data drives and dedicated parity drivesQuickly replaced by RAID 5
71 RAID Level 5 Disk striping with distributed parity Distributes data and parity evenly across the drivesRequires at least three drivesMost common RAID implementationSoftware-based RAID 5
72 RAID 5 (Stripe with Parity) Decimal2221204213Decimal2120Odd Parity2131Data1Data1Parity
73 RAID Level 6 Super disk striping with distributed parity RAID 5 with asynchronous and cached data capabilityThe 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 PATAPATA allowed only four drivesSATA today viewed as comparable choiceSpeeds comparable to SCSIDedicated SATA controllers can support up to 15 drives
75 Hardware vs. Software Hardware RAID Software RAID Dedicated controller Operating system views it as single volumeSoftware RAIDOperating system recognizes all individual disksCombines 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-inThe future is RAIDRAID has been around for 20 years but is now less expensive and moving into desktop systems
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