User manual OCTEK GLOSSARY

[. . . ] GLOSSARY A ACCESS ­ (v) Read, write, or update information stored on a disk or other medium. (n) The operation of reading, writing, or updating stored information. ACCESS TIME ­ The interval between the time a request is made by the system and the time the data is available from the drive. Includes the seek time, rotational latency, and command processing overhead time. [. . . ] A non dedicated file server can be used simultaneously as a file server and a workstation. FIRMWARE ­ Permanent instructions and data programmed directly into the circuitry of readonly memory for controlling the operation of the computer. Distinct from software, which can be altered by programmers. FLUX DENSITY ­ The number of magnetic field patterns that can be stored in a given length of disk surface. The number is usually stated as flux changes per inch (FCI), with typical values in the thousands. (See also FCI. ) G GIGABYTE (GB) ­ One billion bytes (one thousand megabytes). GUIDE RAILS ­ Plastic strips attached to the sides of a hard disk drive in an IBM PC/AT or compatible computer so that the drive easily slides into place. H HALF-HEIGHT ­ Standard drive size equivalent to half the vertical space of a 5 1/4-inch drive. HARD DISK ­ A type of storage medium that retains data as magnetic patterns on a rigid disk, usually made of an iron oxide or alloy over a magnesium or aluminum platter. Because hard disks spin more rapidly than floppy disks, and the head flies closer to the disk, hard disks can transfer data faster and store more in the same volume. HARD ERROR ­ A data error that persists when the disk is re-read, usually caused by defects in the physical surface. HARD-SECTORED ­ The most common method of indicating the start of each sector on a disk, based on information located in the embedded Viking 2. 27/4. 55S G-3 Glossary servo. This method is more precise than softsectored techniques and results in lower overhead. (See also soft-sectored. ) HEAD ­ The tiny electromagnetic coil and metal pole used to create and read back magnetic patterns on the disk. HEAD CRASH ­ Damage to the read/write head, usually caused by sudden contact with the disk surface. Head crash can also be caused by dust and other particles. HIGH-CAPACITY DRIVE ­ By industry conventions typically a drive of 100 megabytes or more. HIGH-LEVEL FORMATTING ­ Formatting performed by the operating system to create the root directory, file allocation tables and other basic configurations. (See also low-level formatting. ) HOME ­ Reference track used for recalibration of the actuator. HOST ADAPTER ­ A plug-in board that acts as the interface between a computer system bus and the disk drive. by, and then the next is read. It would take three revolutions of the disk to access a full track of data. Quantum drives have an interleave of 1:1, so a full track of data can be accessed within one revolution of the disk, thus offering the highest data throughput possible. INTERNAL DRIVE ­ A drive mounted inside one of a computer's drive bays, or a hard disk on a card installed in one of the computer's expansion slots. J JUMPER ­ A tiny box that slips over two pins on a circuit board, connecting the pins electrically. [. . . ] STEPPER ­ A type of motor that moves in discrete steps with each electrical pulse. Stepper were originally the most common type of actuator engine, since they can be geared to advance a read/write head one track per step. However, they are not as fast, reliable, or durable as the voice coil actuators found in Quantum disk S SCSI ­ Small Computer System Interface. An interface designed for Apple Macintosh systems and UNIX workstations. [. . . ]