Understanding and Supporting Hard Drives

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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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Types of Hard Drive Interfaces

• EIDE standards
• Other interface standards
• SCSI
• IEEE 1394
• Fibre Channel

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IDE Channels on a Motherboard
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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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IDE Technology

• Most hard drives use IDE standards

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Tracks and Sectors on IDE Drive

• Older MFM and RLL technologies
• Have either 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 the same
  throughout the platter
• Tracks near center have smallest number of
  sectors per track

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Older Technologies
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Zone Bit Recording
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IDE Drives

• Low-level formatting
• Track and sector markings are written on hard
  drive at the factory
• High-level formatting (OS formatting)
• Executed by the OS
• Creating a boot sector, FAT, and root directory

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Hard Drive Manufacturers
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Communicating with the Hard Drive BIOS

• Calculating drive capacity on older drives
• Adjusting for more complex hard drive
  organization
• Calculating capacity on newer drives
• CHS or normal mode
• Translation methods
• ECHS mode or large mode
• LBA mode

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Calculating Drive Capacity on Older Drives
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Installations Using Legacy BIOS

• Let the BIOS see the drive as a smaller drive
• Upgrade the BIOS
• Upgrade entire motherboard
• Use software that interfaces between older BIOS
  and large-capacity drive
• Use an adapter card that provides the BIOS to
  substitute for system BIOS

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How System BIOS Helps Manage Data Transfer

• Provides interrupt handler for software
  interrupts
• Automatically detects/configures hard drive
• Helps manage data transfer over I/O bus between
  hard drive and memory
• Using PIO mode, CPU is in charge
• Using DMA with DMA controller in charge (no CPU
  involvement)
• With bus mastering using DMA, hard drive BIOS
  controls data transfer

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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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How a Hard Drive Is Logically Organized to Hold
Data

• Steps for preparing a hard drive to hold files
  (after physical installation)
• Low-level format
• Partition hard drive
• High-level format

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Hard Drive Partitions and Logical Drives

• Partitions
• High-level divisions
• Logical drives (volumes)
• Further division of partitions
• Have letters assigned to them
• Each has its own file system (eg, FAT16, FAT32)

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Drive Partitions and Logical Drives
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Contents of a Partition Table
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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 these
  file system items at beginning of each logical
  drive
• OS boot record
• FAT
• Root directory

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Layout for the Boot Record
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Disk Type and Descriptor Byte
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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
• Plan drive configuration
• Prepare work area and take precautions

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Prepare 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

• Format C/S
• Format D
• Format E

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Managing and Troubleshooting Hard Drives

• Error messages
• Tools for troubleshooting and maintaining hard
  drive
• Solving common hard drive problems
• General troubleshooting guidelines

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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
• 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

• Computer recently moved?
• New hardware recently installed?
• New software recently installed?
• Software recently reconfigured or upgraded?
• History of similar problems?

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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

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Chapter Summary

• Hard drive technology
• Communicating with hard drive BIOS
• Logical organization of a hard drive
• Installing and troubleshooting hard drives
• Importance of good backups