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 • 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 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 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 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 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
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
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
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
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
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 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
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
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