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Magnetic Storage

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Tells the drive head to read or write. 7. How a Hard Disk Drive Works ... The hard drive controller sends the logical geometry to the system BIOS ... – PowerPoint PPT presentation

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Title: Magnetic Storage


1
Magnetic Storage
  • CIS 145
  • Microcomputer Servicing
  • Kelvin Kempfer

2
Magnetic Storage
  • The Hard Disk Drive (HDD)
  • How Disk Space is Organized
  • Hard Drive Size Limitations
  • Hard Disk Drive Interfaces
  • How to solve hard drive installation problems

3
The Hard Disk Drive (HDD)
  • Hard Drive
  • Primary computer storage device
  • Secondary Memory
  • Spins, reads and writes one or more fixed disk
    platters
  • Storage medium in desktop and laptop computers
  • The term hard differentiates high-capacity
    rigid disks made aluminum or glass from
    low-capacity floppy disks made of plastic

4
First Microcomputer Hard Disk Seagate introduced
the first hard disk for personal computers in
1979. At 5MB, the ST506 held 10 times as much as
the RAMAC at a fraction of its size. (Image
courtesy of Seagate Technology, Inc.)
5
The Hard Disk Drive (HDD)
  • A sealed metal housing.
  • Protection against dust particles
  • An electrical motor connected to a spindle
  • Spends as many as 8 magnetically coated platters
  • Todays platters are coated with an alloy about
    three millionths of an inch thick
  • Several thousand revolutions/minute

6
How a Hard Disk Drive Works
  • Logic board receives commands from the drives
    controller.
  • Managed by the operating system and BIOS
  • Translates commands into voltage fluctuations
  • Forces the head actuator to move read/write
    heads
  • Makes sure the spindle turning the platters is at
    a constant speed
  • Tells the drive head to read or write

7
How a Hard Disk Drive Works
  • A head actuator pushes and pulls the read/write
    heads across the surfaces of the platters with
    critical precision.
  • Aligns heads with the tracks

8
How a Hard Disk Drive Works
  • Read/write heads slide in unison across both the
    top and bottom surfaces of the platters.
  • Write the data coming from the disk controller by
    aligning the magnetic fields of particles
  • Read the data by detecting the polarities of
    particles that have already been aligned

9
Spindle
Actuator
Platters or disks
Read/write head
10
  • Have one, two, or more platters
  • Stack together
  • Spin in unison

Platters or disks
11
How Disk Space is Organized
  • When a disk is manufactured,
  • Its surface is on a large area.
  • An organizational structure must be imposed that
    uniquely names each physical location on the
    disk
  • Drive controller can specify the exact physical
    spot where a given bit of data should be written
    or retrieved
  • Cylinders, Heads, Sectors , and Tracks
  • CHS

12
How Disk Space is Organized
  • Each side or surface of one hard drive platter is
    called a head.
  • The number of heads in the same as the number of
    disk platter surfaces available for writing data
  • Almost all magnetic disks are double-sided
  • There is a separated read/write head for each
    side.
  • The numbering starts at the bottom side of the
    bottom platter with 0.
  • An average number of heads for a hard disk today
    is 16.

13
How Disk Space is Organized
  • A track is a combination of the cylinder and head
    location over the writeable portion of the hard
    disk.
  • In a multiplatter or multiside disk, each side
    has its own separate tracks
  • A 1.44MB floppy disk has 40 tracks per side
  • A large hard disk can have tens of thousands

14
How Disk Space is Organized
  • A sector is the smallest unit that can be read
    from or written to a disk.
  • Pie slices made by lines that cross over the
    track lines.
  • Each sector holds exactly 512 bytes of data
  • Modern 1.44MB floppy disks use 36 sectors/track
  • A typical IDE hard drive usually has 63
    sectors/track
  • A SCSI hard drive can have 600 or more sectors
    per track

15
How Disk Space is Organized
  • Cylinders are the concentric writeable tracks
    found on the surface of the platters that make up
    the hard drive.
  • The stack of tracks accessible at a given
    position constitutes a cylinder.
  • The number of cylinders a drive has in the same
    as the number of tracks on a single disk side
  • All areas of a disk at a certain in/out head
    position on all disk sides combined

16
(No Transcript)
17
How Disk Space is Organized
  • Calculating the capacity of the drive
  • Cylinders x heads x sectors/track x 512
    bytes/sector
  • Divide by
  • 1024 KB
  • 1048576 MB
  • 1073741824 GB (Typical size)

18
Hard Drive Size Limitations
  • Three possible settings in most BIOS Setup
    programs (translations)
  • CHS (Cylinder, Head and Sector) Mode or Normal
    Mode
  • Extended CHS Mode (ECHS) or Large Mode
  • Logical Block Addressing (LBA)

19
Hard Drive Size Limitations
  • CHS (Cylinder, Head and Sector) Mode or Normal
    Mode
  • The addressing is the same coming into and going
    out of the BIOS
  • Straight pass-through
  • This setting turns off any translation and limits
    the drive size to 528MB
  • A drive can have no more than 1,024 cylinders, 16
    heads, 63 sectors per track and 512 bytes per
    sector

20
Hard Drive Size Limitations
  • Extended CHS Mode (ECHS) or Large Mode
  • This was the original type of translation
  • Used for drives between 504 MB and 8.4 GB
  • The hard drive controller sends the logical
    geometry to the system BIOS
  • Logical geometry presents information not exactly
    equal to the physical geometry yields the actual
    capacity of the drive
  • Controller BIOS masks the actual organization of
    the drive from system BIOS and software (White
    Lie)
  • Large mode is not as popular as LBA

21
Hard Drive Size Limitations
  • 3. Logical Block Addressing (LBA)
  • LBA is the most popular way of dealing with large
    drives if the OS is using system BIOS to access
    the drive.
  • Most popular way of dealing with drives larger
    than 504 MB
  • Only way of dealing with drives larger than 8.4
    GB.
  • Drives larger than 504 MB are called
    large-capacity drives
  • Motherboard BIOS that support them is called
    enhanced BIOS
  • Simply views the drive as a long list of
    sequential numbers

22
Hard Drive Size Limitations
  • You may need a BIOS update if
  • Your BIOS was made before 1996
  • Does not support ECHS or LBA
  • A BIOS between 1996 and 1998
  • Might support LBA but not have Enhanced BIOS
    Services for Disk Drives support

23
Hard Drive Size Limitations
  • Enhanced BIOS Services for Disk Drives
  • Introduced in 1998
  • Breaks the 8 GB barrier
  • Supports drives up to 18 trillion gigabytes
  • A BIOS feature not a drive feature

24
Hard Drive Size Limitations
  • Device Drivers
  • Used to bypass the system BIOS
  • Communicates directly with the hard drive
    controller
  • Windows NT/2000/XP uses this method
  • Windows 9x has its own 32-bit, protected-mode
    device drivers to access hard drives
  • Can also support system BIOS

25
Hard Drive Size Limitations
  • If you install an old drive that has been using
    Standard CHS into a new system that autodetects
    it and sets it up to use LBA, you could lose
    access to the existing data on that drive. In
    such case you would manually configure the drive
    in BIOS to use Standard CHS, retrieve its data
    and then switch it over to LBA and repartition it.

26
Hard Drive Size Limitations
  • Other BIOS settings
  • Multisector transfers
  • Specifies the number of sectors in each block
    transfer from the hard drive to memory
  • Disabled, 2, 4, 8, or 16
  • 16 is usually the right setting
  • Self-Monitoring and Reporting Tool (SMART)
  • A technology for monitoring drive performance and
    reporting any irregularities or changes that
    might signal impending failure.

27
Hard Drive Performance
  • Timing
  • Access time
  • The average amount of time it takes for the
    read/write head to move to the requested sector
  • The sum of seek time and latency period
  • Seek time
  • The average time it takes the read/write head to
    move to the requested track
  • Latency period
  • The time it takes for the requested sector to
    spin underneath the read/write head after the
    read/write head moves to the requested track

28
Hard Drive Performance
  • Timing
  • Data Transfer rate
  • Determined according to the method by which data
    are transferred to and from the platters.
  • Bits/second or Bytes/second
  • Dependent on the speed of the disk and the
    density of the data on the disk

29
Formatting
  • Low-Level Formatting
  • The process that defines the tracks and sectors
    on the platters of the hard drive
  • High-Level Formatting
  • The process of writing the file system structure
    on the disk so that it can be used to store
    programs and data
  • The disk can be made bootable by copying the
    operating systems boot files

30
Hard Disk Drive Interfaces
  • EIDE (Enhanced Integrated Device Electronics)
  • ANSI (American National Standards Institute)
  • An extension of IDE (Integrated Drive
    Electronics)
  • Standard defining how hard drives relate to the
    system
  • Tape drives, CD-ROM and Zip drives
  • First standard was ATA-2
  • Allows up to four devices
  • ATAPI Advanced Technology Attachment Packet
    Interface)

31
Hard Disk Drive Interfaces
  • EIDE
  • IDE/ATA (1988)
  • Speeds range from 2.1MB/s to 8.3 MB/s
  • Limited to no more than 528 MB
  • Supports PIO and DMA
  • 40-pin ribbon cable
  • Introduced the Identify Drive command
    (autodetect)
  • ATA-2/Fast ATA (1996)
  • Speeds up to 16.6 MB/s
  • Breaks the 528 MB barrier
  • Allows up to four IDE devices
  • Supports PIO and DMA transfer modes
  • ATA-3 (Improved version of ATA-2) (1997)
  • SMART

32
Hard Disk Drive Interfaces
  • EIDE (continued)
  • Ultra ATA, Fast ATA-2, Ultra DMA, DMA/33
  • ATA-4
  • Speeds up to 33.3 MB/s
  • Defined a new DMA mode but only supports slower
    PIO modes
  • Supported 80-wire ribbon caable
  • Introduced ATAPI standard
  • Ultra ATA/66, Ultra DMA/66
  • ATA-5
  • Speeds up to 66.6 MB/s
  • Uses an 80-conductor cable
  • Improves signal integrity

33
Hard Disk Drive Interfaces
  • EIDE (continued)
  • Ultra ATA/100
  • Speeds up to 100 MB/s
  • Uses an 80-conductor cable
  • Ultra ATA/133
  • Speeds up to 133 MB/s
  • Supports drives larger than 137 GB
  • Uses an 80-conductor cable
  • ATA/ATAPI-6
  • A part of the ATA/133 standard that supports
    drives larger than 137 GB.

34
Features 60/80/100/120G Available 60G
formatted Capacity Per disk Ultra ATA - 100
FDB (Fluid Dynamic Bearing) Motor
Load/Unload Technology GMR Head Technology
with Wireless Suspension Design SilentSeek
Silentec Hybrid Latch Technology
35
Hard Disk Drive Interfaces
  • EIDE Cabling Methods
  • Parallel ATA (PATA)
  • 80-conductor
  • Looks similar to the 40-conductor
  • Fits the same 40-pin IDE connector
  • Has twice the number of conductors when compared
    to the 40-conductor
  • Serial ATA cable
  • Fewer pins than a parallel cable
  • Fasted than ATA/100
  • More expensive

36
Hard Disk Drive Interfaces
37
Hard Disk Drive Interfaces
  • Transfer Modes
  • Obsolete
  • Programmed Input/Output
  • DMA
  • UltraDMA (UDMA)
  • Also known as UltraATA

38
Hard Disk Drive Interfaces
  • Transfer Modes
  • Programmed Input/Output
  • Five different modes (0 - 4)
  • PIO-0 (3.3 MB/s)
  • PIO-4 (16.67 MB/s)

39
Hard Disk Drive Interfaces
  • Transfer Modes
  • Direct Memory Addressing (DMA)
  • Regular
  • Uses DMA controller on the mother board
  • Bus Mastering
  • Higher speed DMA functionality built into the
    south bridge of the chipset
  • Takes advantage of the PCI bus for DMA transfers
  • Modes 0 - 2 (4.16 - 16.67 MB/s)

40
Hard Disk Drive Interfaces
  • Northbridge Connects CPU to RAM, AGP bus, PCI
    Express bus, Built-in display Adapter
    Southbridge Connects CPU to ATA (IDE) Drives,
    USB bus, FireWire bus, Serial port, Parallel
    port, Built-in audio, ISA bus (earlier PCs)

41
Hard Disk Drive Interfaces
  • Transfer Modes
  • UltraDMA (UDMA)
  • Also known as UltraATA
  • A high-speed transfer mode for disk drives that
    improves upon DMA and allows transfer rates of up
    to 100MB/s
  • Enable UltraDMA and it does the rest

42
Hard Disk Drive Interfaces
  • When a modern BIOS autodetects a modern IDE
    drive, it will set the PIO/DMA to Disabled
    because it employs UltraDMA instead. You should
    not attempt to enable PIO or DMA on such a drive
    because it will only slow it down.

43
Reading a File from Disk
  • User makes a request
  • Chooses Drive
  • Operating System checks Virtual File Allocation
    Table (VFAT)
  • FAT16
  • FAT32
  • NTFS

44
Reading a File from Disk
  • From the VFAT it gets the address of the first
    cluster that contains the beginning of the file
    along with addresses of any other clusters that
    might be used to store the file.

VFAT File 1st Cluster Mom.doc 3 Budget.xls 4
Rock.mp3 5
Cluster Address Cluster Track Sectors 3
1 2,3,4,5 4 1 6,7
,8,9
5 2 1,2,3,4
45
Reading a File from Disk
  • OS provides address information to BIOS
  • BIOS issues commands to the disk drives
    controller
  • Controller moves the read/write head over the
    clusters containing the file.
  • Correct order to read the file from the beginning
    to the end.
  • Data is read from the disk through the BIOS.
  • BIOS places data in RAM

46
Purchasing a Hard Drive
  • What type of drive do you need?
  • What type of controller do you have?
  • SCSI is faster and more reliable.
  • SCSI is more expensive.
  • Do you have any more connections on your
    controller?
  • Most computers have one or two IDE controllers
    with two connections on each controller.
  • SCSI will allow up to seven devices to be
    connected to one controller.

47
IDE Hard Drive InstallationHardware
  • 1. Screw in the hard drive to the open brackets
    (rails) in the case. This step sometimes requires
    you to create a place to house your hard drive.
    If the computer case cannot accept another hard
    drive, consider purchasing a different case for
    the computer.
  • 2. Connect the ribbon cable to the adapter card,
    lining up pin 1 with the red band on the ribbon
    cable.
  • 3. Insert a power cord coming off the power
    supply to the hard drive.

48
IDE Hard Drive InstallationHardware (cont.)
  • 4. IDE drives must be defined in the CMOS SETUP.
    Some newer motherboards have a built-in
    AUTO-DETECT feature that correctly identifies the
    new hard drive. Older computers require you to
    manually define the hard drive in SETUP.
  • 5. If its an older hard drive, use either Type
    47 or User Defined when setting up the drive.
    Its important to add the cylinders, heads and
    sector information included in the drive. This
    information usually can be found on the back of
    the hard drive.
  • 6. After you restart the computer, the system
    BIOS recognizes the drive. Next, run the DOS
    FDISK program to define partitions, and then
    FORMAT the unit.

49
Installing a Second IDE Hard Drive
  • 1. On the second drive, set the DIP switches so
    that the second drive is set as the slave to
    the older master drive.
  • 2. Screw in the hard drive to the open brackets
    (rails) in the case. This step sometimes requires
    you to create a place to house your hard drive.
    If the computer case cannot accept another hard
    drive, consider purchasing a different case for
    the computer.
  • 3. Connect the ribbon cable to the hard drive,
    lining up pin 1 with the red band on the ribbon
    cable.

50
Installing a Second IDE Hard Drive (cont.)
  • 4. Insert a power cord coming off the power
    supply to the hard drive. IDE drives must be
    defined in the CMOS SETUP. Some newer
    motherboards have a built-in AUTO-DETECT feature
    that correctly identifies the new hard drive.
    Older computers require you to manually define
    the hard drive in SETUP.
  • 5. If its an older hard drive, use either Type
    47 or User Defined when setting up the drive.
    Its important to add the cylinders, heads and
    sector information included in the drive. This
    information usually can be found on the back of
    the hard drive.

51
Installing a Second IDE Hard Drive (cont.)
  • 6. After you restart the computer, the system
    BIOS recognizes the drive. Next, run the DOS
    FDISK program to define partitions, and then
    FORMAT the unit.

52
Hard Disk Partitioning
  • Reduces wasted space on larger hard drives.
  • Cluster size can be as large as 64K.
  • When a file is written, it will consume an entire
    cluster, even if it is only a few bytes in size.
  • An average document file is 14K, but it will use
    an entire cluster. On a very large drive, this
    would waste 50K.

53
CHKDSK.EXE and ScanDisk
  • Prior to MS-DOS 6.0, you could use a utility
    called CHKDSK.EXE. This utility is used to
    recover lost allocation units and to repair
    cross-linked files.
  • ScanDisk utility does the same as CHKDSK, but it
    also includes a program that will scan the
    surface of your disk for defects and attempt to
    repair them.

54
Defrag
  • Defrag is a hard disk utility that gets rid of
    any file fragments that are on the drive.
  • Fragmented files slow down hard drive access.
  • Defrag can move all the free space together on
    the drive. This is very helpful when creating
    swapfiles.

55
Troubleshooting IDE Hard DrivesPossible Causes
  • Hard drive configuration in CMOS is incorrect
  • Virus on hard drive
  • Incorrect or loose cabling of the hard drive to
    the controller
  • Corrupt or defective boot sector or partition
  • MS-DOS corrupted
  • Invalid entry in the AUTOEXEC.BAT or CONFIG.SYS
    file
  • Hardware conflict caused by the addition of a new
    piece of hardware

56
Hard Drive Error Codes and Possible Solutions
  • Hard disk configuration error
  • Check CMOS
  • Loose cable
  • Hard disk 0 failure
  • Check CMOS
  • Check power supply to the hard drive
  • Hard disk controller failure
  • Loose controller cable
  • Invalid drive specification
  • Check CMOS

57
Hard Drive Error Codes and Possible Solutions
(cont.)
  • Error selecting drive
  • Check CMOS
  • Check FDISK partition
  • Invalid command interpreter
  • Check CMOS
  • Reload MS-DOS to the boot sector
  • No boot device available
  • Check CMOS
  • Reload MS-DOS to the boot sector

58
Hard Drive Error Codes and Possible Solutions
(cont.)
  • Missing operating system
  • Check CMOS
  • Reload MS-DOS to the boot sector
  • General Failure reading drive C or Not ready
    reading drive C
  • Check CMOS
  • Run CHKDSK or SCANDISK

59
Floppy Drives
  • First PC floppy drive could hold only 160K.
  • PC/XT came with a 5.25-inch 360K.
  • Largest capacity for a 5.25-inch is 1.2MB.
  • Do not attempt to format a 360K diskette to
    1.2MByou will have multiple bad sectors, and if
    you write data to the disk, you run the risk of
    losing the data.

60
Floppy Drives (cont.)
  • The first 3.5-inch was introduced in the late
    1980s and could hold 720KB.
  • A hard plastic case and a spring-loaded cover
    protects the disk. This results in a longer life
    expectancy over the 5.25-inch floppy disks.
  • 3.5 inch diskettes can now store up to 2.88MB,
    but the norm is 1.44MB.
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