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.)
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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

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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

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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

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

Platters or disks
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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

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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.

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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

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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

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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

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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)

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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)

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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

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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

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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

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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

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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

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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

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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.

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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.
  

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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

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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

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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

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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)

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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

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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

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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.

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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
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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

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Hard Disk Drive Interfaces
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Hard Disk Drive Interfaces

• Transfer Modes
• Obsolete
• Programmed Input/Output
• DMA
• UltraDMA (UDMA)
• Also known as UltraATA

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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)

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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)

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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)

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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

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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

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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
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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

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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.
  

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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.
  

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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.

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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.
  

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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.

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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.

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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.
  

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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.

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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.
  

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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
  

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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

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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

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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

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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.

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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.