B. Hard Disk Drives Chapter 9, Lesson 1 Floppy Disk Drives



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Chapter 9, Basic Disk Drives

|1| Chapter Overview

A. Floppy Disk Drives

B. Hard Disk Drives


Chapter 9, Lesson 1

Floppy Disk Drives

|2| 1. The Basics of Floppy Disk Drives

A. The first floppy disk was an 8-inch floppy developed by IBM in 1972.

B. The 5.25-inch disk (160 KB and 1.2 MB), introduced with the PC in 1981, is now obsolete.

C. The 3.5-inch disk is the current technology.

1. 1.44-MB capacity is the current standard; data is stored on both sides of the magnetic disk, using high density.

2. The 2.88-MB disk is not commonly used in today’s PC’s.

D. Both disk drives use a 34-lead ribbon cable but use different power plugs and voltages.

E. The 5.25-inch drive uses a Molex connector for power.

F. The 3.5-inch drive uses a mini connector.

G. After you install a new floppy disk drive in an older computer, you might have to use the basic input/output system (BIOS) to adjust the proper settings for type and position.

|3| 2. Keeping a Floppy Disk Drive Running

  1. Floppy disk drives are usually rugged but are susceptible to failure because their internal components are exposed to environmental conditions and foreign objects.

  2. Schedule monthly cleanings for best performance.

  3. If a floppy disk drive doesn’t work, check the floppy disk first.

1. Ensure that the floppy disk is not write protected. If two or more disks are unreadable, the floppy disk drive might be bad.

2. Data errors caused by a defective floppy disk usually result in an “Abort, Retry, Fail” error message.

D. Check complementary metal-oxide semiconductor (CMOS) settings for problems that might cause the following errors:

1. General failure reading drive A (or B)

2. Not ready error reading drive A (or B)

3. Insert disk for A (or B) and press any key when ready

E. Check or change the floppy disk drive cable.

F. Change the floppy disk drive controller.

1. If an on-board controller fails, disable it and add an expansion card.

  1. Replacing the motherboard is less expensive than repairing the floppy disk drive.

G. Replace the floppy disk drive as needed and discard the malfunctioning drive.



Chapter 9, Lesson 2

Hard Disk Drives

|4| 1. Physical Characteristics

A. The first form of PC mass storage was magnetic tape (cassette tape).

1. Easily damaged

2. Time-consuming to locate specific data on the tape because it was stored sequentially in no specific order

B. The first IBM hard disk drive, called a fixed disk, was introduced in the late 1970s.

1. The PC-XT was the first PC to include a hard disk drive.

2. Was the forerunner of all PC fixed disks

C. Hard disk drive components are housed in a sealed case.

1. Platters

2. R/W heads

3. Actuator arm

|5| 2. Storing Data

A. Data is stored on the drive using binary code.

1. On magnetic media, 1s and 0s are stored as either magnetic or nonmagnetic areas on the drive surface.

2. Flux reversal is the transition between magnetized and nonmagnetized positions on the drive surface.

B. Encoding methods

1. FM

a. Based on timing

b. Each 0 or 1 is preceded by a timing bit.

2. MFM

a. Uses the preceding data bit to indicate whether the current bit is 1 or 0

b. Reduces the number of timing bits required by more than 50 percent

3. RLL

a. Current technology

b. Eliminates timing bits

c. Uses patterns of 1s and 0s to represent longer patterns of 1s and 0s

|6| 3. Actuator Arms

A. The actuator arm holds R/W heads in place.

B. Speed and accuracy are critical elements.

C. Two technologies

1. Stepper motor: older technology that had the following disadvantages:

a. Required slippage to be kept to a minimum

b. Deterioration over time caused data transfer errors.

c. Heat negatively affected the operation of the stepper motor.

d. R/W heads needed to be “parked” when not in use.

2. Voice coil motor: newer technology

    1. Advantages:

(1) Lack of mechanical interface between motor and actuator
(2) Self-parking drives

b. Disadvantage: the need to use one side of the platter (head) for mapping

D. Head-to-disk interference (HDI) means head crash.

1. Occurs when the R/W head comes into contact with the surface of the platter

2. Handle a hard disk drive carefully and appropriately to avoid HDI.

|7| 4. Geometry

  1. The geometry of a hard disk drive is the organization of data on the platters.

  2. Geometry involves five numerical values:

1. Heads

2. Cylinders

3. Sectors per track

4. Write precompensation

5. Landing zone

  1. The five geometry values are changed in the BIOS in two ways: manually, or automatically recognized by the system.

  2. The number of heads is relative to the total number of sides of all platters.

1. The BIOS limits the maximum number of heads to 16.

2. If the actuator arm uses a voice coil motor, one or two heads may be reserved for accuracy of the arm position.

3. Sector translation allows some hard drives to have more than two heads per platter.

E. Cylinders intersect all platters in circular paths.

1. Set of tracks of the same diameter through each platter

2. The maximum number of cylinders is 1024.

F. A track is a circular path on the surface of each platter.

G. Sectors are like a slice of a pie.

1. Each sector holds 512 bytes of data.

2. 63 sectors per track

H. Obsolete values:

1. Write precompensation

2. Landing zone

I. Maximum CHS (cylinders, heads, and sectors) values:

1. 1024 cylinders

2. 16 heads

3. 63 sectors per track

4. 512 bytes per sector

J. The maximum hard disk drive size (504 MB) can be exceeded by

1. Bypassing the BIOS by using a BIOS on the hard disk controller

2. Changing the way the system BIOS routines are read

|8| 5. Hard Disk Drive Types

A. The ST-506 was the first hard disk drive standard for PCs, developed by Seagate in 1980.

  1. ESDI was introduced by Maxtor in 1983.

1. Moved functions to the hard disk drive

2. Became obsolete due to its high cost and advances in other drive technologies

C. IDE and EIDE were introduced in the 1990s.

1. IDE integrated the benefits of both ST-506 and ESDI.

2. EIDE added a number of improvements to the standard IDE drive.

a. Increased data throughput

b. Support for other storage devices

c. Uses up to four IDE devices instead of just two

d. Support for hard disk drives larger than 528 MB

3. EIDE is the standard for most hard disk drives in today’s PCs.

D. SCSI was developed in the 1970s.

1. Is the most robust hard disk drive interface

2. Is popular on network servers and high performance workstations

3. Originally allowed up to seven peripheral devices to be daisy chained to one common bus

4. SCSI-2 supports up to 15 devices.

5. SCSI adapters use their own BIOS and firmware to communicate with devices, offloading some load from the system bus.

6. Uses one of two software interface layers to communicate with the operating system (OS):

a. Common Access Method (CAM) is now obsolete.

b. Advanced SCSI Programming Interface (ASPI) drivers are included with all Microsoft Windows OSs.

7. Allows both internal and external connections on the same adapter

|9| 6. Installation and Setup

  1. Installing a hard disk drive involves the following steps:

1. Physical installation and cabling

2. CMOS setup

3. Low-level formatting

4. Partitioning

5. High-level formatting

|10| 7. Physical Installation and Cabling

A. ST-506

1. Uses a 34-connector control cable and a 20-connector data cable for each drive

2. The twist in the control cable determines which hard disk drive is drive 0 and which is drive 1.

B. IDE/EIDE

  1. Uses a simple 40-pin cable

2. Does not have a twist in the cable

3. IDE supports two drives configured as master/slave.

4. Jumpers are generally used to designate the master drive and the slave drive.

C. Ultra DMA/66

1. Uses a special version of the 40-pin IDE cable

2. Has a blue connector on one end and a black connector on the other

|11| 8. Setting the System CMOS for the Hard Drive

A. Geometry values must be entered correctly in the CMOS.

B. Earlier CMOS versions allowed two drives, and later versions allow up to four drives.

  1. Other devices besides hard disk drives can be added but must be configured correctly (CD-ROM, CD-R, tape).

1. An important consideration is whether the customer plans to upgrade the system in the future.

2. Only hard disk drives should be placed on the primary IDE channel, if possible.

3. A CD-ROM (or tape drive) can be configured as the master (primary) on the second channel (or the slave on either channel).

|12| D. There are over 45 preset types for CHS values.

1. The user type allows for manual entry of the values.

E. Most CMOS chips have an IDE autodetection setting.

F. If the wrong information is entered into the CMOS system, it might not recognize the entire drive.

G. Determining the geometry of a hard disk drive

1. Check the label.

2. Check the hard disk drive documentation.

3. Contact the manufacturer.

H. The hard disk drive must be assigned a drive name or letter.

1. The MS-DOS and Windows drive 0 is C, and 1 is D.

2. Drive letters may change when you add more drives.

3. The only fixed drive letters are A, B, and C.

|13| 9. Low-Level Formatting

  1. Has three simultaneous functions:

1. Creates and organizes the sectors

2. Sets the proper interleave

3. Establishes the boot sector

B. Low-level formatting is not required on IDE and Ultra DMA drives. SCSI drives are low-level formatted using a built-in utility.

C. IDE drives use a special type of low-level formatting called embedded servo.

1. Is done by the manufacturer

2. Can also be done with a special utility provided by the manufacturer

|14| 10. Preparing the New Drive

A. Create a bootable disk with the following:

1. Use FORMAT A: /S to copy system files to the disk.

2. Copy FORMAT.COM (or FORMAT.EXE) and FDISK.COM.

B. Create a Windows 98 startup disk by going to Add/Remove Programs in Control Panel.

C. Use the bootable disk to partition and format the new drive.

|15| 11. Partitioning

A. Partitions

1. Divide the disk into several drive letters to organize data

2. Allow more than one OS to be accommodated

B. The primary partition stores the boot information for the OS.

C. The extended partition

1. Is for a hard disk drive (or part of a hard disk drive) that does not have an OS

2. May contain logical partitions within it

D. Use fdisk to partition a newly installed hard disk after the CMOS has been properly configured.

  1. Disk drives larger than 4 GB might be limited on older systems.

1. Disk access is limited to the largest size recognized by that system.

F. The active partition and the primary partition are not necessarily the same thing.

1. The primary partition stores boot information for the computer.

2. The active partition contains the OS files.

3. The boot partition on advanced OSs contains a boot manager that

a. Marks the selected OS as active

b. Starts the OS located in that partition

|16| 12. High-Level Formatting

A. FORMAT.COM

1. Creates and configures the FATs

2. Creates the root directory

B. FAT

1. The base storage unit of a drive is a sector (512 bytes maximum).

2. The FAT is an index that tracks which part of a file is stored on which sector.

3. Each partition or floppy disk drive has two FATs stored near the beginning of the partition: FAT#1 and FAT#2.

4. The index has the address to the first part of a file.

5. If a file is stored over several sectors, each subsequent piece contains information linking it to the next. The last piece is marked with an end-of-file code.

|17| C. FAT32

1. Less wasted space; can use smaller cluster sizes on larger partitions

2. Can create a partition up to 2 terabytes (TB)

3. Considerations for using FAT32:

a. Do not use on dual boot systems shared by other OSs that do not support FAT32.

b. FAT32 partitions that are shared can be read across the network.

c. FAT32 does not support compression.

d. Do not use disk utilities that are not made for FAT32.

|18| 13. Fragmentation and Disk Compression

A. A hard disk can become fragmented over time for several reasons.

1. When a file is saved to the hard disk drive, the file system tries to keep all clusters together. This allows for fast retrieval.

2. The continual addition and deletion of files begins to leave open clusters, so empty spaces remain between existing files.

3. Open clusters are filled by the first part of the next file to be saved.

4. Files soon become fragmented, or scattered, all over the drive, which slows retrieval.

B. Defragmentation programs can reorganize information and improve speed on the hard disk drive.

1. DEFRAG, an MS-DOS program, cannot rewrite or move systems and hidden files.

2. Microsoft Windows 95, Microsoft Windows 98, and Microsoft Windows Me include a defragmentation program.

C. Disk compression

1. Saves space by

a. Eliminating wasted cluster space used by separate disk files

b. Replacing sequences of identical characters with a special reference that represents the actual data

2. May introduce risks

3. Is less necessary because of the advent of large hard disk drives and file systems with smaller cluster sizes

4. Does not work on FAT32

|19| 14. Maintaining a Disk Drive

A. Routine preventive maintenance

1. Perform comprehensive, regularly scheduled backups.

2. Save a copy of the boot sector and partition table information.

B. Have the following tools on hand for hard disk repairs:

1. List of the hard disk drive’s parameters and CMOS settings

2. Bootable floppy disk with fdisk, format, and the correct version of chkdsk and other disk utilities and diagnostics

3. Drivers for any primary expansion cards

4. Good cables for other drives

C. Use only disk tools that are certified for the hard disk drive and the OS.

|20| 15. Common Errors and Troubleshooting Utilities

  1. Errors

1. The Abort, Retry, Fail error is the most common drive error.

2. Connectivity problems usually appear at bootup.

3. Lost boot and partition information may require you to repartition the drive, reload the OS, and restore data from a backup copy.

4. Maintain proper documentation of settings to resolve CMOS errors.

  1. Utilities

1. Scandisk performs a battery of tests on the hard disk and fixes problems.

a. Searches for invalid filenames, invalid file dates and times, bad sectors, and invalid compression structures

b. In the file system, scandisk looks for lost clusters, invalid clusters, and cross-linked clusters.

c. Should be run regularly to help prevent problems

2. Keep paper documentation of your CMOS settings.

3. Use the SCSI BIOS disk utility on a SCSI drive to verify media.

|21| Chapter Summary

A. Floppy disk drive technology has changed little over the years.

B. Floppy disk drives fail more often than any other computer component.

C. Installing a hard disk drive requires you to partition the drive, set the CMOS settings, and format the drive.

D. The fdisk utility is used to create partitions.

E. The geometry (CHS values) of a hard disk drive determines its storage capacity.

F. Partition types include primary, extended, logical, and active.

G. The active partition is used to initialize the OS.




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