Introduction to hard drives
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Introduction to Hard Drives. Chapter 6 - Key Terms. Information Compiled by Diane Ferris, Michele Henderson & Vicki Kertz. Hard Drive Technologies. IDE EIDE SCSI. Integrated Device Electronics. Enhanced Integrated Device Electronics. Small Computer Systems Interface. IDE Drives.

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Introduction to hard drives

Introduction to Hard Drives

Chapter 6 - Key Terms

Information Compiled by Diane Ferris, Michele Henderson & Vicki Kertz


Hard drive technologies

Hard Drive Technologies

IDE

EIDE

SCSI

Integrated Device Electronics

Enhanced Integrated Device Electronics

Small Computer Systems Interface


Ide drives

IDE Drives

  • Hard drive whose disk controller is integrated into the drive, eliminating the need for a controller cable and thus increasing speed, as well as reducing price.

  • Uses an IDE 40-pin data cable and 4-pin power cable.


Eide drives

EIDE Drives

Newer drive standard that allows systems to recognize drives larger than 504 MB and to handle up to four devices on the same controller.


Scsi technology

SCSI Technology

Faster system-level interface with a host adapter and a bus that can daisy chain as many as seven or 15 other devices.


Scsi terms

SCSI Terms

A number from 0 to 15 assigned to each SCSI device attached to a daisy chain.

SCSI ID

SBAC

Embedded SCSI

Terminating Resistor

Termination

SCSI Bus Adapter Chip The chip mounted on the logic board of a hard drive that allows the drive to be a part of a SCSI bus system.

Devices that contain their own host adapter, with the SCSI interface built into the device.

The resistor added at the end of a SCSI chain to dampen the voltage at the end of the chain.

A process necessary to prevent an echo effect of power at the end of a SCSI chain resulting in interference with the data transmission.


Scsi device drivers

SCSI Device Drivers

Advanced SCSI Programming Interface – A popular device driver that enables operating systems to communicate with a SCSI host adapter. (The “A” originally stood for Adaptec.)

ASPI

CAM

Common Access Method – A standard adapter driver used by SCSI


Types of formatting

Low-level format

High-level format

A process (usually performed at the factory) that electronically creates the hard drive cylinders and tests for bad spots on the disk surface.

Format performed by the OS that writes a file system to a logical drive. For DOS and Windows 9x, the command used is FORMAT, which writes a FAT and a directory to the drive. Also called OS format.

Types of Formatting


Hard drive partitions

Partition

Partition table

MBR

Logical Drive

A division of a hard drive that can be used to hold logical drives.

A table at the beginning of the hard drive that contains information about each partition on the drive.

The first sector on a hard drive, which contains the partition table and other information needed by BIOS to access the drive.

A portion or all of a hard drive partition that is treated by the operating system as though it were a physical drive containing a boot record, FAT and root directory.

Hard Drive Partitions


Modes

CHS

ECHS

LBA

The traditional method where BIOS reads and writes to hard drives by addressing the correct cylinder, head and sector (CHS). Also called normal mode.

Extended CHS - Addresses information on hard drives ranging from 504 MB to 8.4 GB, by translating CHS information in order to break the 528 MB HD barrier. Also called large mode.

Logical Block Addressing – Where the BIOS and OS view the drive as one long linear list of LBAs or addressable sectors, permitting drives to be larger than 8.4 GB.

Modes


Introduction to hard drives

Translation

Physical Geometry

Logical Geometry

Enhanced BIOS

A technique used by system BIOS and HD controller BIOS to break the 504 MB HD barrier. This allows a different set of drive perimeters to communicate to the OS and other software than that used by the hard drive controller BIOS.

Actual layout of heads, tracks, and sectors on a hard drive.

The number of heads, tracks, and sectors that the BIOS on the hard drive controller presents to the system BIOS and the OS. Doesn’t consist of the same values as the physical geometry.

A newer BIOS that has been written to accommodate larger-capacity gigabyte drives.

Mode Terms


Dos commands

MKDIR

CHDIR

RMDIR

TREE

ATTRIB

MIRROR

UNFORMAT

Used to create a directory on a drive

Changes the current default directory.

Used to remove an unwanted directory. You must delete all files in the directory prior to using.

Shows the disk directories in a graphical layout.

Displays or changes the read-only, archive, system and hidden attributes to files.

Saves partition table info to disk when used with /PARTN parameter.

Reverses the effect of accidental formats and repairs a damaged partition table if it was saved with MIRROR /PARTN command.

DOS Commands


Fragmentation and clusters

Fragmentation

Defragment

Cross-Linked Clusters

Lost Clusters

CHKDSK /F

Distribution of data files, such that they are stored in noncontiguous clusters.

To “optimize” or rewrite a file to a disk in one contiguous chain of clusters, thus speeding up data retrieval.

Errors caused when files appear to share the same disk space, according to the FAT.

Lost file fragments that, according to the FAT, contain data that does not belong to any file.

CHKDSK /F can free lost file fragments.

Fragmentation and Clusters


Compression

Disk Compression

Data Compression

Compressed Drive

CVF

Drive Space

Compressing data on a hard drive to allow more data to be written to the drive.

Reducing the size of files by various techniques such as using a shortcut code to represent the repeated data.

A drive whose format has been reorganized to store more data; not a drive, but a type of file, typically with a host drive called H.

Compressed Volume File – File on the host drive of a compressed drive that holds all compressed data.

A utility that compresses files so that they take up less space on a disk drive, creating a single large file on the disk to hold all the compressed files.

Compression


Disk caching

SMARTDrive

VCACHE

A hard drive Cache program that comes with Win 3.x and DOS that can be executed as a TSR from the AUTOEXEC.BAT file.

A built-in Win 9x 32-bit software cache that doesn’t take up conventional memory space or upper memory space, as SMARTDrive does.

Disk Caching


Introduction to hard drives

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