IDE and SCSI Devices

Terms and Definitions

Chapter Objectives

After completing this chapter you will:

• Understand hard drive terminology.

• Understand the different hard drive types.

• Be able to set up and configure different types of hard drives.

• Be able to troubleshoot hard drive problems.

• Understand and be able to perform hard drive preventive maintenance.

Hard Drive Overview

• Hard drives are the most popular devices for storing data. The hard

drive subsystem can have up to three parts:

– The hard drive

– Cables that attach to an adapter or the motherboard

– Control circuits located on an adapter or the motherboard

Hard Drive Geometry

• Components of a Hard Drive:

– Platters are multiple hard metal surfaces contained in the hard drive.

– Read/Write Heads write and read 1s and 0s to and from the hard drive surface.

• A Head Crash occurs when a read/write head touches the hard drive platter.

– Track is a concentric circle on a formatted floppy or hard drive platter.

– Cylinder is one corresponding track on all surfaces of a hard drive.

– Sectors – Each track is divided into sectors which contains 512 bytes of data.

• ZBR (Zone Bit Recording) efficiently uses the hard drive surface by placing more sectors on the outer tracks than on the inner tracks.

• Interleaving is a method of numbering sectors for the most efficient transfer of data between the hard drive and the controller. Today’s hard drives normally use a 1:1 interleave.

Hard Drive Geometry

Hard Drive Geometry

IDE/SCSI – Figure #1

Hard Drive Geometry

Cylinder vs Tracks

IDE/SCSI – Figure #2

Hard Drive Geometry

Sectors on Older Hard Drives

IDE/SCSI – Figure #3

Hard Drive Geometry

IDE/SCSI – Figure #4

Zone Bit Recording Sectors

Hard Drive Geometry

3:1 Interleaving

IDE/SCSI – Figure #5

Hard Drive Interfaces Overview

• There are four hard drive interfaces:

– ST506

– ESDI

– IDE (ATA)

– SCSI

• Encoding is the way 1s and 0s are placed on the drive.

IDE (Integrated Drive Electronics)

• IDE (Integrated Drive Electronics) is the most popular type of hard drive used in home

and business computers.

– DMA (Direct Memory Access) allows data transfer between the hard drive and RAM

without going through the CPU.

– PIO (Programmed Input/Output) is a speed standard for data transfers to and from the

hard drive.

– UDMA (Ultra DMA) allows the IDE interface to control the PCI bus for faster transfers.

– SMART (Self-Monitoring Analysis & Report Technology) is part of the ATA-3 IDE

standard for power management, drive analysis, and failure reporting.

– CRC (Cyclic Redundancy Checking) is an advanced method of checking the data for

errors.

– ATAPI (AT Attachment Packet Interface) is the hardware side of the IDE specification

that supports devices like CD and tape drives.

– Serial ATA is a point to point interface in which each device connects to the host

through a dedicated link and has the entire interface bandwidth.

IDE (Integrated Drive Electronics)

PIO Modes for IDE Hard Drives

IDE/SCSI – Table #1

IDE (Integrated Drive Electronics)

DMA Modes for IDE Hard Drives

IDE/SCSI – Table #2

IDE (Integrated Drive Electronics)

80 and 40 Pin Conductor Cable

IDE/SCSI – Figure #6

IDE (Integrated Drive Electronics)

IDE ATA Standards

IDE/SCSI – Table #4

SCSI (Small Computer System Interface)

• SCSI (Small Computer System Interface) is an interface standard that

connects multiple small devices to the same adapter via a SCSI bus.

– SCSI bus is the bus shared by all devices that attach to one SCSI

adapter.

– Host Adapter connects the SCSI device to the motherboard and

coordinates the activities of other devices connected.

SCSI (Small Computer System Interface)

SCSI Standards

IDE/SCSI – Table #5

Laptop Storage Devices

• Laptops can use IDE or SCSI hard drives.

• Laptop IDE hard drives are installed using two methods:

– Proprietary installation is installed in a location that cannot be

changed, configured, or moved very easily.

– Removable IDE hard drives with a laptop are installed or removed

through a 44-pin connector.

SCSI Software Standards

• Most SCSI hard drives have software built into the hard drive’s BIOS

chip. Other drives must use one of three types of SCSI software

standards:

– ASPI (Advanced SCSI Programming Interface)

– CAM (Common Access Method)

– LADDR (Layered Device Driver Architecture)

Drive Configuration Overview

• The configuration of a hard drive usually includes setting jumpers on the

drive, terminating properly, and performing a few software commands.

IDE Device Configuration

• IDE Hard Drives are normally configured using jumpers.

– Single IDE setting is used when only one devices connects to the IDE cable.

– Master IDE setting is a jumper setting used to configure an IDE device and is

the controlling device on the interface.

– Slave IDE setting is an IDE setting for the second device added to the IDE

cable. The device should be a slower device than the master.

– Cable Select is a setting used on IDE devices when a special cable

determines which device is the master and which one is the slave.

– DASP (Drive Active/Slave Present) is a signal in the ATA interface of the

IDE connector that is used to indicate the presence of a slave IDE device.

– Master/Slave configuration can be found on 9-19.

IDE Device Configuration

IDE Motherboard Connectors

IDE/SCSI – Figure #7

IDE Device Configuration

IDE Hard Drive Set as Master

IDE/SCSI – Figure #8

IDE Device Configuration

Two IDE Hard Drives

IDE/SCSI – Figure #9

Serial ATA (SATA) Installation

• Serial ATA drives are easy to install.

– Serial ATA drives do not have any master/slave, cable select, or

termination settings

– Uses a small 7-pin connector that attaches between the serial ATA

controller and the serial ATA drive

• Installation instructions for serial ATA drives can be found on 9-25.

Serial ATA (SATA) Installation

Installed SATA Hard Drive and Adapter

IDE/SCSI – Figure #12

SCSI Configuration

• A SCSI device is configured by:

– Setting the proper SCSI ID

– Terminating both ends of the SCSI chain

– Connecting the proper cables

• A SCSI ID is the priority number assigned to each device connected by a

SCSI chain.

SCSI ID Configuration

• Standard SCSI devices recognize SCSI IDs 0 through 7.

• Wide SCSI devices recognize SCSI IDs 0 through 15.

• Power on all external SCSI devices before powering on the computer.

• Each SCSI device must have a unique SCSI ID.

– SCAM (SCSI Configured AutoMatically) allows for automatic SCSI

ID assignment.

SCSI ID Configuration

SCSI ID Settings (Most Significant Bit to the Left)

IDE/SCSI – Table #7

SCSI ID Configuration

Two Internal SCSI Devices – SCSI IDs

IDE/SCSI – Figure #13

SCSI ID Configuration

Two External SCSI Devices – SCSI IDs

IDE/SCSI – Figure #14

SCSI Termination

• SCSI termination is performed in several different ways:

– By installing a SIPP

– By installing a jumper

– By setting a switch

– By installing a terminator plug

– By installing a pass-through terminator

– Through software

SCSI Termination

• The SCSI bus cannot operate properly without terminating both ends of the SCSI bus.

– SE (Single Ended) is a type of SCSI electrical signal and terminator used with most SCSI devices.

– Passive Terminators are one type of SCSI chain end that is susceptible to noise interference over long cable distances. It is used with SCSI-1 devices.

– Active Terminators are a type of end to a SCSI chain that allows for longer cable distance and provides correct voltage for SCSI signals.

– FPT (Forced Perfect Termination) is a special type of active terminator that can be used with SE devices.

– HVD (High Voltage Differential) is a SCSI-2 standard that allowed longer SCSI bus lengths and required a differential terminator. HVD was removed from the SCSI-3 standards.

– Differential Terminator is a SCSI terminator used with HVD SCSI devices. It cannot be used with other SCSI types.

– LVD (Low Voltage Differential) is a SCSI signaling type that is required on all SCSI devices that adhere to the Ultra SCSI standards. LVD is backwards compatible with SE.

– Pass Through Terminator allows a device that does not have terminators to be terminated through the connector that attaches to the cable.

SCSI Termination

SCSI Termination

IDE/SCSI – Figure #15

SCSI Termination

Today’s SCSI Terminators:

Pass Through Terminator and 68-Pin Active Terminator

IDE/SCSI – Figure #17

SCSI Termination

SCSI Symbols

IDE/SCSI – Figure #19

SCSI Termination

Two Internal SCSI Devices - Termination

IDE/SCSI – Figure #20

SCSI Termination

Two External SCSI Devices - Termination

IDE/SCSI – Figure #21

SCSI Termination

Internal and External SCSI Devices - Termination

IDE/SCSI – Figure #22

SCSI Cables

• SCSI cabling allows multiple devices to be connected to one SCSI host

adapter and share the same SCSI bus.

– Most internal SCSI-1 and SCSI-2 cables are 50-pin ribbon cables.

They are also known as an A cable.

– Internal SCSI-3 cables are 68-pin ribbon cables.

• When installing multiple SCSI devices, install one device at a time.

• Always avoid using the cheaper, thinner SCSI cables. They are more

susceptible to outside noise.

SCSI Cables

Internal SCSI Cables

IDE/SCSI – Figure #23

SCSI Cables

External SCSI Cables

IDE/SCSI – Figure #24

SCSI Cables

SCSI Cables and Connectors

IDE/SCSI – Table #9

System Configuration for Hard Drives

• Hard drives are configured through the Setup program with a drive type

number.

– Drive Type is a number that corresponds to a drive’s geometry (the

number of cylinders, heads, and sectors).

– IDE hard drives are normally configured using the Auto-Detect feature

included with BIOS. This feature automatically determines the drive

type for the system.

BIOS Configurations for Hard Drives

• Most system BIOS chips manufactured before 1994 use INT13 to

recognize hard drives up to 504MB.

– INT13 Interface or Interrupt 13 is a standard that allows a system

BIOS to locate data on the hard drive.

– LBA (Logical Block Addressing) allows hard drives to be

recognized up to 8GB in capacity.

– Extended INT13 Interface can support drives larger than 8GB in

capacity.

Hard Drive Preparation Overview

• Three steps to hard drive preparation:

– Low-Level Format

– Partition

– High-Level Format

Partitioning

• Partitioning divides a hard drive so that the computer system sees more than

one drive.

– FDISK is a command used to partition a hard drive.

• A File System defines how data is stored on a drive.

– FAT (File Allocation Table) is a method of organizing a computer’s file

system.

– FAT16 file system is supported by DOS, Windows 9x, NT, 2000, and XP.

– FAT32 file system used by Windows 95 Service Release 2, Windows 98,

Windows 2000, and XP that supports hard drives up to 2TB in size.

– NTFS (NT File System) file system used with Windows NT, 2000, and XP.

Partitioning

• Types of Partitions:

– The Primary Partition is the first detected drive on the hard drive.

– The Extended Partition is a hard drive division

– Logical Drives divides the extended partition into separate units which appear as separate drive letters.

– System Partition is a type of active hard drive partition found in Windows NT and 2000 that contains the hardware-specific files needed to load the operating system.

– Boot Partition – A type of partition found in Windows NT and 2000 that contains the operating system.

• The Partition Table holds the information about the types and locations of partitions created. It is part of the master boot record.

• MBR (Master Boot Record) is a program that reads the partition table to find the primary partitions used to boot the system.

Partitioning

Clusters

IDE/SCSI – Figure #25

Partitioning

FAT16 Partitions and Cluster Size

IDE/SCSI – Table #12

Partitioning

FAT32 Partitions and Cluster Size

IDE/SCSI – Table #13

Partitioning

NTFS Partitions and Cluster Size

IDE/SCSI – Table #14

Partitioning

NT Disk Administrator

IDE/SCSI – Figure #26

Partitioning

Hard Drive Partitioning

IDE/SCSI – Figure #27

Partitioning

Two Logical Drives

IDE/SCSI – Figure #28

How Drive Letters Are Assigned

• The order in which the partitions are assigned drive letters depends on

three factors:

– The number of hard drives

– The type of partitions on the hard drives

– The operating system

• The first floppy drive detected is assigned drive letter A:.

• The second floppy drive detected is assigned drive letter B:.

• The first hard drive primary partition detected receives drive letter C:.

• Drive letters assigned after letter C: are dependent upon the operating

system installed.

How Drive Letters Are Assigned

Logical Drive Letters with Two Hard Drives

IDE/SCSI – Figure #30

Windows 2000/XP Logical Disk Management

• Windows 2000 and XP have two types of storage: Basic and Dynamic.

– Basic Storage is a Windows 2000 term for a partition.

• Basic Disk is a Windows 2000 term for a drive that has been

partitioned and formatted.

– Dynamic Storage is a Windows 2000 disk that has been configured

for the 2000 operating system.

• Dynamic Disk is a Windows 2000 term for volumes that can be

resized and managed without rebooting.

• Volume is a hard drive term used to describe all of a hard drive or hard

drive portions that have been combined into one unit.

Windows 2000/XP Logical Disk Management

• Dynamic disks can have different types of volumes:

– Simple Volume is disk space allocated from one hard drive.

– Spanned Volume is disk space created from multiple hard drives.

– Striped Volume is when data is written across two to thirty-two hard

drives.

– Raid 5 Volume puts data on three or more hard drives and one of the

hard drive spaces is used for parity.

– System Volume holds the files needed to boot the operating system.

– Boot Volume holds the remaining operating system files. The

system volume and the boot volume can be one and the same.

Fault Tolerance

• RAID (Redundant Array of Independent (formerly Inexpensive) Disks allows

writing to multiple hard drives for larger storage areas, better performance, and

fault tolerance.

• Fault Tolerance is the ability to continue functioning after a hardware or software

failure.

• Different RAID levels

– RAID Level 0 is also called disk striping without parity. It does not protect

data when a hard drive fails.

– RAID Level 1 is called disk mirroring or disk duplexing.

• Disk mirroring uses two or more hard drives and one disk controller.

• Disk duplexing uses two or more hard drives and two disk controllers.

– RAID Level 5 is also called disk striping with parity. It writes data to three or

more hard drives and includes parity information with the data.

High-Level Format

• The last step in preparing a hard drive for use is high-level formatting.

– High-Level Format is the process that sets up the file system for use

by the computer.

• DBR (DOS Boot Record) is area of a disk that contains system files.

• Boot Sector was previously called DBR. This section of a disk contains

information about the system files.

High-Level Format

FAT16 and NTFS Volume Structure

IDE/SCSI – Figure #32

Bootable Disks

• A user should have a startup disk for each operating system supported.

– ERD (Emergency Repair Disk) is a copy of the REPAIR folder

created when backing up the registry in Windows 2000 Professional

and NT Workstation. This can help when the operating system has

problems booting.

Bootable Disks

Boot Files

IDE/SCSI – Table #17

Viruses

• A Virus is a program written to cause a device not to operate in its

normal fashion.

• Common types of viruses include:

– BIOS virus

– Boot sector (MBR) virus

– File virus

– Macro virus

– Trojan Horse Programs

– Worm virus

Viruses

Virus Types

IDE/SCSI – Table #18

Logically Troubleshooting Newly Installed Drives

• Problems with new drive installations:

– Improper jumper configuration

– SCSI ID settings

– Termination

– Problems with cabling

– Drive type configuration

Logically Troubleshooting Previously Installed Drives

• Problems with hard drives that worked previously:

– Check for viruses

– Check for resource conflicts from any new hardware or software that

was installed

– Check for loose cables

– Verify bootable system files

– Verify that the hard drive is still operational

IDE Specific Errors

• Problems with IDE hard drives:

– Verify Pin 1 connection on the cable to Pin 1 connection on the drive

– Verify the master and slave jumper settings

– Verify the correct CMOS settings for the drives

– Verify if an 80 conductor cable is required.

SCSI Specific Errors

• Problems with SCSI hard drives:

– Check for incorrect termination

– Check the SCSI ID for the drives

– Check the SCSI adapter’s resources assigned

Autoexec.bat and Config.sys Errors

• To troubleshoot CONFIG.SYS and AUTOEXEC.BAT problems, step

through one command or driver at a time.

Preventive Maintenance for Hard Drives

• Preventive Maintenance will prolong the life of the computer.

– CHKDSK is a program that locates clusters disassociated from data

files.

• Lost Clusters are sectors on a disk that the file allocation table

cannot associate with any file or directory.

– SCANDISK is a software program used to detect and repair lost

clusters.

– Disk Cleanup is a Windows 2000 utility that helps free up hard drive

space by emptying the Recycle Bin, removing temporary files, etc.

Hard Drive Fragmentation

• Over time files will become fragmented on a hard drive and slow down

access time.

– Defragmentation is the process of placing files in contiguous sectors.

This allows for faster hard disk access of files.

Hard Drive Fragmentation

Fragmented Hard Drive

IDE/SCSI – Figure #34

Disk Caching/Virtual Memory

• Ways to speed up the hard drive:

– Disk Cache or Data Buffer is a portion of RAM set aside for hard

drive data that speeds up hard drive operations.

– VMM (Virtual Memory Manager) is a Windows component that

uses hard disk space as if it were RAM.

• It is best to put the swap file on a the fastest hard drive that doesn’t

contain the operating system.

• Virtual memory swap file size can be adjusted.