Computers and Networking Systems

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Computers and Networking Systems

• Class 4.2

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Chapter 7

• Understanding and Supporting Hard Drives

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You Will Learn

• About hard drive technologies
• How communication with hard drive BIOS is
  accomplished
• How a hard drive is logically organized to hold
  data
• How to install a hard drive
• How to troubleshoot hard drives

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Hard Drive Technology

• Technology of how the hard drive interfaces with
  the system
• Technology used within the hard drive to read and
  write data to the drive

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The EIDE Interface Standards

• Define how hard drives and other drives relate to
  the system
• Drives other than hard drives can use EIDE if
  they follow ATAPI (Advanced Technology Attachment
  Packet Interface)
• Specify data transfer speed more than any other
  single factor
• Most popular ANSI standard is Ultra ATA/100

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EIDE Standards

• Support two IDE connections, a primary and a
  secondary
• Each connection can support up to two IDE devices
  for a total of four devices on a system
• Possible configurations
• Primary IDE channel, master device
• Primary IDE channel, slave device
• Secondary IDE channel, master device
• Secondary IDE channel, slave device

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IDE Channels on a Motherboard
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Other Interface Standards

• SCSI
• Second most popular interface
• IEEE 1394
• Uses serial transmission
• Popular for multimedia and home entertainment
• Also called FireWire or i.Link
• Fibre Channel
• For high-end systems with multiple hard drives
• Faster than SCSI, but expensive

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How Hard Drives Work

• Platter(s) are stacked together and spin in
  unison
• Read/write heads are controlled by an actuator
  and move in unison across disk surfaces as disks
  rotate on a spindle
• Require hard drive controller for instructions

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Hard Drive with Four Platters
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Hardware Subsystem Including an IDE Hard Drive
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Tracks and Sectors on IDE Drive

• Older MFM and RLL technologies
• Have 17 or 26 sectors per track over entire drive
  platter
• All tracks contain same number of bytes
• IDE drives use zone bit recording formatting
  system
• Number of sectors per track is not same
  throughout platter
• Tracks near center have smallest number of
  sectors per track
• OS cannot communicate with IDE drive by
  contacting hard drive controller BIOS and using
  sector/track coordinates

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Older Technologies
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Zone Bit Recording
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Low-Level Formatting

• Track and sector markings are written on hard
  drive at the factory
• IDE drives cannot be low-level formatted as part
  of preventive maintenance
• OS does high-level formatting by executing
  remainder of the format process (creating boot
  sector, FAT, and root directory)

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Adjusting for More Complex Hard Drive Organization

• CHS (cylinder, head, sector) mode or normal mode
  for drives less than 528 MB
• Large mode or ECHS (extended CHS) for drives
  between 504 MB and 8.4 GB
• LBA (logical block addressing) mode for drives
  larger than 504 MB
• OS and software can bypass system BIOS and
  communicate directly with controller BIOS using
  device drivers

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How a Hard Drive Is Logically Organized to Hold
Data

• Requirements to boot from hard drive and get to a
  command prompt
• Drive must have track and sector markings written
  on it
• A file system must be installed
• Files needed to boot the PC must be copied to
  root directory of drive

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Preparing a Hard Driveto Hold Files

• Low-level format
• Partition hard drive
• High-level format

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Hard Drive Partitions

• High-level divisions
• Partition table is 512 bytes long and occupies
  one sector
• Active partition
• Partition of hard drive used to boot OS
• Contains only a single logical drive (drive C)
• Always the first partition on the drive

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Contents of a Partition Table
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Logical Drives (Volumes)

• Further division of partitions (primary and
  extended)
• Have letters assigned to them
• Each has its own file system (eg, FAT16, VFAT,
  FAT32)

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Hard Drive Partitions
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How Many Logical Drives?

• Use multiple logical drives to optimize space and
  access time to the drive
• The larger the drive, the larger the cluster
  size, and the more slack or wasted space
• Goal is to use as few logical drives as possible
  and still keep cluster size to a minimum
• Use Fdisk, Diskpart, or Disk Management to create
  logical drives

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How Many Logical Drives?
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How Many Logical Drives?

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When to Partition a Drive

• When installing a new hard drive
• If existing hard drive is giving errors
• If you suspect a virus has attacked the drive
• To wipe hard drive clean and install new OS

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What Happens During Formatting

• OS format for each logical drive creates
• OS boot record
• FAT
• Root directory

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Installing a Hard Drive

• Set jumpers or DIP switches on drive physically
  install drive inside case attach power cord and
  data cable
• Inform CMOS setup of new drive, or verify that
  autodetect correctly detected the drive
• Use Fdisk utility to create partition(s) on
  drive divide extended partition into logical
  drives
• Use Format command to high-level format each
  logical drive
• Install OS and other software

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Prepare for Installation

• Read documentation
• Have a good bootable disk or Windows 9x rescue
  disk available
• Plan drive configuration
• Prepare work area and take precautions

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Preparing for Installation
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Set Jumpers and DIP Switches
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Set Jumpers and DIP Switches
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Set Jumpers and DIP Switches
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Mount Drive in the Bay
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Mount Drive in the Bay
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Mount Drive in the Bay
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Mount Drive in the Bay
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Mount Drive in the Bay
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Mount Drive in the Bay
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Mount Drive in the Bay
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If Bay Is Too Large
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Use CMOS Setup to Change Hard Drive Settings
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Use CMOS Setup to Change Hard Drive Settings
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Use CMOS Setup to Change Hard Drive Settings
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Use CMOS Setup to Change Hard Drive Settings
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Use Fdisk to Partition a Drive
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Use Fdisk to Partition a Drive
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Use Fdisk to Partition a Drive
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Format Each Logical Drive

• Use these commands
• Format C/S
• Format D
• Format E

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A Note on Moving a Hard Drive or Changing BIOS

• Back up data on the drive before you move it
• If BIOS on new computer does not let you access
  data on the drive, you can partition and format
  the drive again, and then move the backed-up data
  onto the newly formatted drive
• Dont change options in setup unless you are sure
  of what you are doing

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An Ounce of Prevention

• Make backups and keep them current
• Run antivirus software regularly
• Defragment files scan hard drive occasionally
• Dont smoke around the hard drive
• Dont leave PC turned off for weeks/months at a
  time
• High humidity can be dangerous for hard drives
• Be gentle with a hard drive

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Commands to Usewith Hard Drives

• Fdisk
• Format
• Defrag and Windows Disk Defragmenter to detect
  and repair fragmentation
• ScanDisk to correct cross-linked and lost clusters

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Lost and Cross-Linked Clusters
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ScanDisk fromCommand Prompt
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ScanDisk from the Desktop
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Resolving CommonHard Drive Problems

• Describe/reproduce the problem?
• Computer recently moved?
• New hardware or software recently installed?
• Software recently reconfigured or upgraded?
• History of similar problems?
• Anyone else recently use the computer?

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Common Hard Drive Problems

• Computer will not recognize newly installed hard
  drive
• Hardware problems
• Hard drive not found
• Invalid drive or drive specification
• Damaged boot record
• Damaged FAT or root directory or bad sectors
• Cannot boot from hard drive
• Drive retrieves and saves data slowly

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Getting Technical Support

• Before you call
• Drive model and description
• Manufacturer and model of computer
• Exact wording of error message, if any
• Description of problem
• Hardware and software configuration for the system