| Access
Time |
The
interval between the time a request is made by the system and
the time the data is available from the drive. |
| Active
copper |
A
Fibre Channel connection that allows copper cabling up to 33
meters (36 yards) in length between devices. |
| Areal
Density |
The
amount of data that's stored on a hard disk per square inch,
and equal to the tracks per inch multiplied by the bits per
inch along each track. |
| Alias
server |
A
proposed standard as part of FC-GS-3. |
| Allocation
|
The
process of assigning particular areas of the disk to specific
data or instructions. An allocation unit is a group of sectors
on the disk reserved for specified information. On hard disks
for small computer systems, the allocation unit is usually in
the form of a sector, block, or cluster. (See also allocation
unit.) |
| Allocation
Unit |
An
allocation unit, also known as a cluster, is a group of sectors
on the disk that can be reserved for the use of a particular
file. |
| AL_PA |
Arbitrated
Loop Physical Address. |
| AL_TIME |
Arbitrated
Loop Timeout value. |
| ANSI |
American
National Standards Institute. A standards-setting, non-government
organization that develops and publishes standards for voluntary
use in the United States. |
| ARB
|
Arbitrative
Primitive Signal. |
| Arbitrated
Loop |
A
shared 100/200-megabytes-per-second Fibre Channel transport
supporting up to a maximum of 126 devices and 1 attachment to
a Fabric. Ports with lower AL_PAs have higher priorities. |
| Arbitration |
Method
of gaining orderly access to a shared-loop topology. |
| ARP |
Address
Resolution Protocol. |
| ASIC |
Application-Specific
Integrated Circuit. |
| ATA/ATA-1
(Advanced Technology Attachment) |
ATA
is the official name given to the IDE interface by ANSI. |
| ATA-2/Fast
ATA-2 |
ATA-2
is also known as EIDE. ATA-2 includes DMA mode 1, and PIO mode
3. Fast ATA-2 includes upgrades in DMA and PIO modes. |
| ATA-3 |
ATA-3
is an update to the ATA-2 standard. It includes SMART capability. |
| ATA-4 |
ATA-4
is an update to the ATA-3 standard. It includes UltraDMA capability. |
| ATM |
Asynchronous
Transfer Mode. |
| AV
Drive |
Audio
Video drive: a disk drive that is optimized for audio and video
applications. Transferring analogue high-fidelity audio and
video signals onto a digital disk and playing them back at high
performance levels requires a drive that can sustain continuous
reads and writes without interruption. AV drives are designed
to avoid thermal recalibration during reading and writing so
that lengthy transfers digital video data will not be interrupted,
and frames will not be lost. |
| Bad
Block |
A block
of memory that cannot reliably hold data due to a physical flaw or normal
wear and tear. |
| Bandwidth |
The transmission capacity
of the cable, link, or system.
|
| Block |
In UNIX
workstation environments, the smallest contiguous area that can be allocated
for the storage of data. UNIX blocks are generally 8 Kbytes (16 sectors)
in size. In DOS environments, the block is referred to as a cluster. (Note:
This usage of the term block at the operating system level is different
from its meaning in relation to the physical configuration of the hard drive.
See Sector for comparison.) |
| Boot
code |
Software
that initialized the system environment during the early phase of the boot
up process. |
| Boot
flash |
Flash (temporary)
memory that stores the boot code and boot parameters. |
| Buffer
|
An area
of memory reserved for temporary storage of data that is waiting to be sent
to a device that is not yet ready to receive it. |
| Burst
Transfer Rate |
The
maximum amount of data per second a drive can supply intermittently; this
is limited by the system interface. |
| Bus
|
The part
of a chip, circuit board, or interface designed to send and receive data. |
| Bypass
circuitry |
Circuits
that automatically remove a device from the data path when valid signals
are dropped. |
| Cache |
Specialized
high-speed memory used to optimize data transfers between system elements
with different performance characteristics, e.g., disk to main memory or
main memory to CPU. |
| Cache
Memory |
A temporary data storage
area outside the user-accessible area. A cache memory is usually faster
to access than the medium and thus has the effect of increasing data throughput
by reducing the number of accesses to the medium.
|
| CAM |
Content
addressable memory. |
| CDR |
Clock and
data recovery circuitry. |
| CE |
Conformité
Européenne. |
| Channel |
A point-to-point
link whose task is to transport data from one point to another. |
| Cluster |
In
DOS environments, the smallest contiguous area that can be allocated for
the storage of data. DOS clusters are usually 2 Kbytes (4 sectors) in size. |
| Compact
Flash |
Flash (temporary)
memory that is used in a manner similar to hard disk storage. |
| Compact
PCI (cPCI) |
CompactPCI
is a very high performance industrial bus based on the standard PCI electrical
specification in rugged 3U or 6U Eurocard (VME) packaging. Contrary to its
desktop cousin, a CompactPCI board uses a high quality 2 mm metric pin and
socket connector that meets IEC and Bellcore standards. CompactPCI boards
are inserted from the front of the chassis, and the I/O can break out either
to the front or through the rear. |
| Controller |
A computer
module that interprets signals between a host and a peripheral device. |
| COS |
Class of
service. |
| cPCI |
See Compact
PCI. |
| CRC |
Cyclic
Redundancy Check-an error detection procedure that identifies incomplete
or faulty data in each sector. |
