Glossary
Quantum Fireball Plus LM 10.2/15.0/20.5/30.0 GB AT G-3
DISK CONTROLLER – A plug-in board, or
embedded circuitry on the drive, that passes
information to and from the disk. The
Quantum disk drives all have controllers
embedded on the drive printed-circuit board.
DISKWARE – The program instructions
and data stored on the disk for use by a
processor.
DMA – Acronym for direct memory access.
A process by which data moves directly
between a disk drive (or other device) and
system memory without passing through the
CPU, thus allowing the system to continue
processing other tasks while the new data is
being retrieved.
DRIVE – Short form of disk drive.
DRIVE GEOMETRY – The functional
dimensions of a drive in terms of the number
of heads, cylinders, and sectors per track.
See also logical format.
E
EE
E
ECC – Acronym for error correction code.
The recording of extra verifying information
encoded along with the disk data. The
controller uses the extra information to
check for data errors, and corrects the errors
when possible.
EMBEDDED SERVO – A timing or
location signal placed on the disk’s surface
on the tracks that also store data. These
signals allow the actuator to fine-tune the
position of the read/write heads.
ENCODING – The protocol by which
particular data patterns are changed prior to
being written on the disk surface as a pattern
of On and Off or 1 and 0 signals.
EXTERNAL DRIVE – A drive mounted in
an enclosure separate from the PC or
computer system enclosure, with its own
power supply and fan, and connected to the
system by a cable.
F
FF
F
FAT – Acronym for file allocation table. A
data table stored on the outer edge of a disk
that tells the operating system which sectors
are allocated to each file and in what order.
FCI – Acronym for flux changes per inch.
See also BPI.
FILE SERVER – A computer that provides
network stations with controlled access to
shareable resources. The network operating
system is loaded on the file server, and most
shareable devices (disk subsystems,
printers) are attached to it. The file server
controls system security and monitors
station-to-station communications. A
dedicated file server can be used only as a file
server while it is on the network. A non
dedicated file server can be used
simultaneously as a file server and a
workstation.
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.
FLYING HEIGHT – The distance between
the read/write head and the disk surface
caused by a cushion of air that keeps the
head from contacting the media. Smaller
flying heights permit more dense storage of
data, but require more precise mechanical
designs.
FORMAT – To write onto the disk surface a
magnetic track pattern that specifies the
locations of the tracks and sectors. This
information must exist on a disk before it
can store any user data. Formatting erases
any previously stored data.
FORMATTED CAPACITY – The amount
of room left to store data on the disk after the
required space has been used to write sector
headers, boundary definitions, and timing
information generated by a format
operation. All Quantum drive capacities are
expressed in formatted capacity.
FORM FACTOR – The physical outer
dimensions of a device as defined by
industry standard. For example, most
Quantum disk drives use a 3 1/2-inch form
factor.
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